diff --git a/x/billing/keeper/keeper.go b/x/billing/keeper/keeper.go
index d637323..e7b188d 100644
--- a/x/billing/keeper/keeper.go
+++ b/x/billing/keeper/keeper.go
@@ -76,6 +76,9 @@ func (k Keeper) GetAuthority() string {
 }
 
 func (k Keeper) SetPlatformValidators(ctx sdk.Context, vals []string) error {
+	if err := types.ValidatePlatformValidators(vals); err != nil {
+		return err
+	}
 	params := k.GetParams(ctx)
 	params.PlatformValidators = vals
 	k.SetParams(ctx, params)
diff --git a/x/billing/types/params.go b/x/billing/types/params.go
index a35792d..4fd1304 100644
--- a/x/billing/types/params.go
+++ b/x/billing/types/params.go
@@ -66,11 +66,22 @@ func validatePlatformValidatorsParam(v interface{}) error {
 	if !ok {
 		return fmt.Errorf("could not unmarshal platform-validators parm for validation")
 	}
+	return ValidatePlatformValidators(vals)
+}
+
+// ValidatePlatformValidators validates that all platform validator addresses are valid
+// and that there are no duplicates.
+func ValidatePlatformValidators(vals []string) error {
+	seen := make(map[string]bool)
 	for _, val := range vals {
 		_, err := sdk.AccAddressFromBech32(val)
 		if err != nil {
 			return fmt.Errorf("invalid platform validator address: %s", val)
 		}
+		if seen[val] {
+			return fmt.Errorf("duplicate platform validator address: %s", val)
+		}
+		seen[val] = true
 	}
 	return nil
 }
diff --git a/x/billing/types/params_test.go b/x/billing/types/params_test.go
new file mode 100644
index 0000000..9248e43
--- /dev/null
+++ b/x/billing/types/params_test.go
@@ -0,0 +1,85 @@
+package types
+
+import (
+	"testing"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/stretchr/testify/require"
+)
+
+func init() {
+	config := sdk.GetConfig()
+	config.SetBech32PrefixForAccount("saga", "sagapub")
+	config.SetBech32PrefixForValidator("sagavaloper", "sagavaloperpub")
+	config.SetBech32PrefixForConsensusNode("sagavalcons", "sagavalconspub")
+}
+
+func TestValidatePlatformValidatorsParam(t *testing.T) {
+	addr1 := "saga14grgksm5pe5u4cf8pvcchfsl8mfg8mvj3c95l0"
+	addr2 := "saga1nkm3et2qcqgya0ad8wt6e20l6206xdtccw28c9"
+	addr3 := "saga1zggrvdnjzsfpc7sr7jnw2jl5v9u8vjn263x0s0"
+
+	tests := []struct {
+		name    string
+		input   interface{}
+		wantErr bool
+		errMsg  string
+	}{
+		{
+			name:    "valid empty list",
+			input:   []string{},
+			wantErr: false,
+		},
+		{
+			name:    "valid single address",
+			input:   []string{addr1},
+			wantErr: false,
+		},
+		{
+			name:    "valid multiple addresses",
+			input:   []string{addr1, addr2},
+			wantErr: false,
+		},
+		{
+			name:    "invalid address format",
+			input:   []string{"invalid-address"},
+			wantErr: true,
+			errMsg:  "invalid platform validator address",
+		},
+		{
+			name:    "duplicate addresses",
+			input:   []string{addr1, addr1},
+			wantErr: true,
+			errMsg:  "duplicate platform validator address",
+		},
+		{
+			name:    "duplicate addresses with valid in between",
+			input:   []string{addr1, addr2, addr1},
+			wantErr: true,
+			errMsg:  "duplicate platform validator address",
+		},
+		{
+			name:    "three unique addresses",
+			input:   []string{addr1, addr2, addr3},
+			wantErr: false,
+		},
+		{
+			name:    "wrong type",
+			input:   "not a slice",
+			wantErr: true,
+			errMsg:  "could not unmarshal platform-validators",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validatePlatformValidatorsParam(tt.input)
+			if tt.wantErr {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tt.errMsg)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}