diff --git a/lib/dialects/abstract/connection-manager.js b/lib/dialects/abstract/connection-manager.js
index 17c0f3d026b6..15597d7cc67b 100644
--- a/lib/dialects/abstract/connection-manager.js
+++ b/lib/dialects/abstract/connection-manager.js
@@ -256,6 +256,10 @@ class ConnectionManager {
             _options.logging.__testLoggingFn = true;
 
             return this.sequelize.databaseVersion(_options).then(version => {
+              if (this.dialectName === 'postgres' && _.isString(version) &&
+                !version.match(/\.\d+\./)) {
+                version += '.0';
+              }
               this.sequelize.options.databaseVersion = semver.valid(version) ? version : this.defaultVersion;
               this.versionPromise = null;
 
diff --git a/lib/dialects/abstract/query-generator.js b/lib/dialects/abstract/query-generator.js
index 12eedd58685d..d57223b2cf41 100755
--- a/lib/dialects/abstract/query-generator.js
+++ b/lib/dialects/abstract/query-generator.js
@@ -128,7 +128,30 @@ class QueryGenerator {
       emptyQuery += ' VALUES ()';
     }
 
-    if (this._dialect.supports.returnValues && options.returning) {
+    if (this.dialect === 'postgres') {
+      if (options.onConflict && semver.gte(this.sequelize.options.databaseVersion, '9.5.0')) {
+        const constraint = options.conflict.constraint;
+        const target = Array.isArray(options.conflict.target) ? options.conflict.target : [options.conflict.target];
+        if (constraint) {
+          valueQuery += ' ON CONFLICT ON CONSTRAINT ' + this.quoteIdentifier(constraint) + options.onConflict;
+        } else if (target) {
+          const conflictTarget = target.map(e => this.quoteIdentifier(e)).join(', ');
+          valueQuery += ' ON CONFLICT (' + conflictTarget + ') ';
+
+          const conflictPredicate = options.conflict.update.where;
+          if (conflictPredicate) {
+            valueQuery += 'WHERE ' + this.whereItemsQuery(conflictPredicate, options) + ' ';
+          }
+
+          valueQuery += + options.onConflict;
+        }
+        valueQuery += ' RETURNING ' + options.returning;
+      } else {
+        options.onConflictFallback = true;
+      }
+    }
+
+    if (this._dialect.supports.returnValues && options.returning && !options.isPgUpsert) {
       if (this._dialect.supports.returnValues.returning) {
         valueQuery += ' RETURNING *';
         emptyQuery += ' RETURNING *';
@@ -251,11 +274,12 @@ class QueryGenerator {
     options = options || {};
     fieldMappedAttributes = fieldMappedAttributes || {};
 
-    const query = 'INSERT<%= ignoreDuplicates %> INTO <%= table %> (<%= attributes %>) VALUES <%= tuples %><%= onDuplicateKeyUpdate %><%= returning %>;';
+    const query = 'INSERT<%= ignoreDuplicates %> INTO <%= table %> (<%= attributes %>) VALUES <%= tuples %><%= onDuplicateKeyUpdate %><%= onConflictKeyUpdate %><%= returning %>;';
     const tuples = [];
     const serials = {};
     const allAttributes = [];
     let onDuplicateKeyUpdate = '';
+    let onConflictKeyUpdate = '';
 
     for (const fieldValueHash of fieldValueHashes) {
       _.forOwn(fieldValueHash, (value, key) => {
@@ -293,12 +317,49 @@ class QueryGenerator {
       }).join(',');
     }
 
+    if (this._dialect.supports.updateOnConflict && options.updateOnConflict) {
+      const { primaryKeyField, rawAttributes } = options.model;
+      options.updateOnConflict = _.extend({
+        constraint: '',
+        target: primaryKeyField,
+        update: {}
+      }, options.updateOnConflict || {});
+      if (!options.updateOnConflict.update.columns) {
+        options.updateOnConflict.update.columns = allAttributes.filter(value => value !== primaryKeyField);
+      }
+
+      const { constraint, target, update } = options.updateOnConflict;
+      let conflict = '';
+      if (constraint) {
+        conflict = ' ON CONFLICT ON CONSTRAINT ' + this.quoteIdentifier(constraint);
+      } else {
+        const targetArr = Array.isArray(target) ? target : [target];
+        const conflictTarget = targetArr.map(e => this.quoteIdentifier(e)).join(', ');
+        conflict = ' ON CONFLICT (' + conflictTarget + ')';
+
+        if (update.where) {
+          conflict += ' WHERE ' + this.whereItemsQuery(update.where, options);
+        }
+      }
+
+      if (update === false) {
+        onConflictKeyUpdate += ' DO NOTHING ';
+      } else {
+        onConflictKeyUpdate += conflict + ' DO UPDATE SET ' + update.columns.map(attr => {
+          const field = rawAttributes[attr] ? rawAttributes[attr].fieldName : attr;
+          const key = this.quoteIdentifier(field);
+          return key + ' = EXCLUDED.' + key;
+        }).join(',');
+      }
+    }
+
     const replacements = {
       ignoreDuplicates: options.ignoreDuplicates ? this._dialect.supports.ignoreDuplicates : '',
       table: this.quoteTable(tableName),
       attributes: allAttributes.map(attr => this.quoteIdentifier(attr)).join(','),
       tuples: tuples.join(','),
       onDuplicateKeyUpdate,
+      onConflictKeyUpdate,
       returning: this._dialect.supports.returnValues && options.returning ? ' RETURNING *' : ''
     };
 
diff --git a/lib/dialects/postgres/index.js b/lib/dialects/postgres/index.js
index 3bb09e4f98e7..e3afb2c6d587 100644
--- a/lib/dialects/postgres/index.js
+++ b/lib/dialects/postgres/index.js
@@ -49,6 +49,7 @@ PostgresDialect.prototype.supports = _.merge(_.cloneDeep(AbstractDialect.prototy
   JSONB: true,
   HSTORE: true,
   deferrableConstraints: true,
+  updateOnConflict: true,
   searchPath: true
 });
 
diff --git a/lib/dialects/postgres/query-generator.js b/lib/dialects/postgres/query-generator.js
index 66b0acc3a74c..96218d013a0b 100755
--- a/lib/dialects/postgres/query-generator.js
+++ b/lib/dialects/postgres/query-generator.js
@@ -342,21 +342,83 @@ class PostgresQueryGenerator extends AbstractQueryGenerator {
   }
 
   upsertQuery(tableName, insertValues, updateValues, where, model, options) {
-    const primaryField = this.quoteIdentifier(model.primaryKeyField);
+    const rawAttributes = model.rawAttributes;
+    const indexes = model.options.indexes;
+    const uniqueKeys = Object.keys(rawAttributes).filter(e => rawAttributes[e].unique);
+    if (!uniqueKeys.length) {
+      uniqueKeys.push(model.primaryKeyField);
+    }
+    const uniqueIndexes = indexes.filter(e => e.unique).map(e => e.name);
+    const uniqueCount = uniqueKeys.length + uniqueIndexes.length;
+    const fields = Object.keys(model.fieldAttributeMap);
+    const fieldMap = {};
+    fields.forEach(field => {
+      fieldMap[model.fieldAttributeMap[field]] = field;
+    });
+
+    if (uniqueCount > 1 && (!options.conflict || options.conflict && !options.conflict.constraint) ||
+      semver.lt(this.sequelize.options.databaseVersion, '9.5.0')) {
+      options.onConflictFallback = true;
+      const primaryField = this.quoteIdentifier(model.primaryKeyField);
+
+      let insert = this.insertQuery(tableName, insertValues, model.rawAttributes, options);
+      let update = this.updateQuery(tableName, updateValues, where, options, model.rawAttributes);
+
+      insert = insert.replace('RETURNING *', `RETURNING ${primaryField} INTO primary_key`);
+      update = update.replace('RETURNING *', `RETURNING ${primaryField} INTO primary_key`);
+
+      return this.exceptionFn(
+        'sequelize_upsert',
+        tableName,
+        'OUT created boolean, OUT primary_key text',
+        `${insert} created := true;`,
+        `${update}; created := false`
+      );
+    }
+
+    const getUpdateArray = (values, target) =>
+      Object.keys(values).map(key => fieldMap[key] || key).filter(value => target.indexOf(value) === -1);
+
+    options.isPgUpsert = true;
+    if (!options.conflict) {
+      options.conflict = {
+        target: uniqueKeys
+      };
+    }
+    if (!options.conflict.update) {
+      options.conflict.update = {
+        columns: getUpdateArray(updateValues, uniqueKeys)
+      }
+    }
+
+    if (options.conflict.update.columns === false) {
+      options.onConflict = ' DO NOTHING';
+    } else {
+      options.conflict.target = options.conflict.target || uniqueKeys;
+      if (!Array.isArray(options.conflict.target)) {
+        options.conflict.target = [options.conflict.target];
+      }
+      options.conflict.target = options.conflict.target.map(key => fieldMap[key] || key);
+      if (!options.conflict.update.columns) {
+        options.conflict.update.columns = getUpdateArray(updateValues, options.conflict.target);
+      }
 
-    let insert = this.insertQuery(tableName, insertValues, model.rawAttributes, options);
-    let update = this.updateQuery(tableName, updateValues, where, options, model.rawAttributes);
+      if (rawAttributes.updatedAt) {
+        insertValues.updatedAt = new Date();
+        if (options.conflict.update.columns.indexOf('updatedAt') === -1) {
+          options.conflict.update.columns.push('updatedAt');
+        }
+      }
+
+      options.onConflict = 'DO UPDATE SET ' + options.conflict.update.columns.map(key => {
+        key = this.quoteIdentifier(key);
+        return key + ' = EXCLUDED.' + key;
+      }).join(', ');
+    }
 
-    insert = insert.replace('RETURNING *', `RETURNING ${primaryField} INTO primary_key`);
-    update = update.replace('RETURNING *', `RETURNING ${primaryField} INTO primary_key`);
+    options.returning = '*, (xmax = 0)::bool AS xmax';
 
-    return this.exceptionFn(
-      'sequelize_upsert',
-      tableName,
-      'OUT created boolean, OUT primary_key text',
-      `${insert} created := true;`,
-      `${update}; created := false`
-    );
+    return this.insertQuery(tableName, insertValues, rawAttributes, options);
   }
 
   deleteQuery(tableName, where, options, model) {
diff --git a/lib/dialects/postgres/query.js b/lib/dialects/postgres/query.js
index 8e517d7768d7..058e15f85eca 100644
--- a/lib/dialects/postgres/query.js
+++ b/lib/dialects/postgres/query.js
@@ -248,7 +248,13 @@ class Query extends AbstractQuery {
         } else if (QueryTypes.BULKDELETE === this.options.type) {
           return parseInt(rowCount, 10);
         } else if (this.isUpsertQuery()) {
-          return rows[0];
+          if (this.options.onConflictFallback) {
+            return rows[0];
+          } else {
+            this.options.fieldMap = this.options.model.fieldAttributeMap;
+            const items = this.options.plain ? rows : this.handleSelectQuery(rows);
+            return [items[0], rows[0].xmax];
+          }
         } else if (this.isInsertQuery() || this.isUpdateQuery()) {
           if (this.instance && this.instance.dataValues) {
             for (const key in rows[0]) {
diff --git a/lib/model.js b/lib/model.js
index fbfe8a4cc613..bc1655441968 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -2285,6 +2285,9 @@ class Model {
       }).then(() => {
         return this.QueryInterface.upsert(this.getTableName(options), insertValues, updateValues, instance.where(), this, options);
       }).spread((created, primaryKey) => {
+        if (primaryKey === true || primaryKey === false) {
+          return options.returning === true ? [created, primaryKey] : primaryKey;
+        }
         if (options.returning === true && primaryKey) {
           return this.findById(primaryKey, options).then(record => [record, created]);
         }
diff --git a/lib/query-interface.js b/lib/query-interface.js
index e1eaf291c050..2036817da9ab 100644
--- a/lib/query-interface.js
+++ b/lib/query-interface.js
@@ -959,13 +959,13 @@ class QueryInterface {
     where = { [Op.or]: wheres };
 
     options.type = QueryTypes.UPSERT;
-    options.raw = true;
+    options.raw = options.isPgUpsert || false;
 
     const sql = this.QueryGenerator.upsertQuery(tableName, insertValues, updateValues, where, model, options);
     return this.sequelize.query(sql, options).then(result => {
       switch (this.sequelize.options.dialect) {
         case 'postgres':
-          return [result.created, result.primary_key];
+          return options.isPgUpsert ? result : [result.created, result.primary_key];
 
         case 'mssql':
           return [
diff --git a/test/integration/model/upsert.test.js b/test/integration/model/upsert.test.js
index 2b32426f37cd..b37fd377d1de 100644
--- a/test/integration/model/upsert.test.js
+++ b/test/integration/model/upsert.test.js
@@ -86,7 +86,8 @@ describe(Support.getTestDialectTeaser('Model'), () => {
       });
 
       it('works with upsert on a composite key', function() {
-        return this.User.upsert({ foo: 'baz', bar: 19, username: 'john' }).bind(this).then(function(created) {
+        const options = { conflict: { constraint: 'users_foo_bar_key' } };
+        return this.User.upsert({ foo: 'baz', bar: 19, username: 'john' }, options).bind(this).then(function(created) {
           if (dialect === 'sqlite') {
             expect(created).to.be.undefined;
           } else {
@@ -94,7 +95,7 @@ describe(Support.getTestDialectTeaser('Model'), () => {
           }
 
           this.clock.tick(1000);
-          return this.User.upsert({ foo: 'baz', bar: 19, username: 'doe' });
+          return this.User.upsert({ foo: 'baz', bar: 19, username: 'doe' }, options);
         }).then(function(created) {
           if (dialect === 'sqlite') {
             expect(created).to.be.undefined;
@@ -142,12 +143,13 @@ describe(Support.getTestDialectTeaser('Model'), () => {
           },
           username: DataTypes.STRING
         });
+        const options = { conflict: { constraint: 'users_pkey' } };
 
         return User.sync({ force: true }).bind(this).then(() => {
           return Promise.all([
             // Create two users
-            User.upsert({ a: 'a', b: 'b', username: 'john' }),
-            User.upsert({ a: 'a', b: 'a', username: 'curt' })
+            User.upsert({ a: 'a', b: 'b', username: 'john' }, options),
+            User.upsert({ a: 'a', b: 'a', username: 'curt' }, options),
           ]);
         }).spread(function(created1, created2) {
           if (dialect === 'sqlite') {
@@ -160,7 +162,7 @@ describe(Support.getTestDialectTeaser('Model'), () => {
 
           this.clock.tick(1000);
           // Update the first one
-          return User.upsert({ a: 'a', b: 'b', username: 'doe' });
+          return User.upsert({ a: 'a', b: 'b', username: 'doe' }, options);
         }).then(created => {
           if (dialect === 'sqlite') {
             expect(created).to.be.undefined;
@@ -268,7 +270,8 @@ describe(Support.getTestDialectTeaser('Model'), () => {
       });
 
       it('works with primary key using .field', function() {
-        return this.ModelWithFieldPK.upsert({ userId: 42, foo: 'first' }).bind(this).then(function(created) {
+        const options = { conflict: { target: 'userId' } };
+        return this.ModelWithFieldPK.upsert({ userId: 42, foo: 'first' }, options).bind(this).then(function(created) {
           if (dialect === 'sqlite') {
             expect(created).to.be.undefined;
           } else {
@@ -276,7 +279,7 @@ describe(Support.getTestDialectTeaser('Model'), () => {
           }
 
           this.clock.tick(1000);
-          return this.ModelWithFieldPK.upsert({ userId: 42, foo: 'second' });
+          return this.ModelWithFieldPK.upsert({ userId: 42, foo: 'second' }, options);
         }).then(function(created) {
           if (dialect === 'sqlite') {
             expect(created).to.be.undefined;
@@ -464,14 +467,15 @@ describe(Support.getTestDialectTeaser('Model'), () => {
         });
 
         return User.sync({ force: true }).then(() => {
-          return User.upsert({ name: 'user1', address: 'address', city: 'City' })
+          const options = { conflict: { target: ['name', 'address'] } };
+          return User.upsert({ name: 'user1', address: 'address', city: 'City' }, options)
             .then(created => {
               if (dialect === 'sqlite') {
                 expect(created).to.be.undefined;
               } else {
                 expect(created).to.be.ok;
               }
-              return User.upsert({ name: 'user1', address: 'address', city: 'New City' });
+              return User.upsert({ name: 'user1', address: 'address', city: 'New City' }, options);
             }).then(created => {
               if (dialect === 'sqlite') {
                 expect(created).to.be.undefined;
@@ -537,7 +541,8 @@ describe(Support.getTestDialectTeaser('Model'), () => {
               // this record is soft deleted
               User.create({ name: 'user3', deletedAt: -Infinity })
             ]).then(() => {
-              return User.upsert({ name: 'user1', address: 'address' });
+              const options = { conflict: { target: ['name', 'deletedAt'] } };
+              return User.upsert({ name: 'user1', address: 'address' }, options);
             }).then(() => {
               return User.findAll({
                 where: { address: null }
@@ -547,6 +552,35 @@ describe(Support.getTestDialectTeaser('Model'), () => {
             });
           });
         });
+
+        it('works with bulkCreate', function() {
+          const User = this.sequelize.define('User', {
+            name: {
+              type: DataTypes.STRING,
+              primaryKey: true
+            },
+            address: DataTypes.STRING
+          });
+
+          return User.sync({ force: true }).then(() => {
+            return User.bulkCreate([
+              { name: 'user1', address: 'user1' },
+              { name: 'user2' }
+            ]).then(() => {
+              return User.bulkCreate([
+                { name: 'user1' },
+                { name: 'user2', address: 'user2' }
+              ], { updateOnConflict: true });
+            }).then(() => {
+              return User.findAll({
+                where: { address: null }
+              });
+            }).then(users => {
+              expect(users).to.have.lengthOf(1);
+              expect(users[0].name).to.equal('user1');
+            });
+          });
+        });
       }
 
       if (current.dialect.supports.returnValues) {