diff --git a/CHANGELOG.md b/CHANGELOG.md
index 742ac45c..a756af72 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Added
+
+- Add test coverage for stac_api_io.py error handling ([#835](https://github.com/stac-utils/pystac-client/pull/835))
+
 ### Changed
 
 - Make `get_collection` raise if `collection_id` is empty ([#809](https://github.com/stac-utils/pystac-client/pull/809))
diff --git a/pystac_client/stac_api_io.py b/pystac_client/stac_api_io.py
index 0daf73e5..479c9c99 100644
--- a/pystac_client/stac_api_io.py
+++ b/pystac_client/stac_api_io.py
@@ -287,7 +287,11 @@ def stac_object_from_dict(
                 d, href=str(href), root=root, migrate=False, preserve_dict=preserve_dict
             )
 
-        raise ValueError(f"Unknown STAC object type {info.object_type}")
+        raise ValueError(
+            f"Unknown STAC object type {info.object_type}"
+        )  # pragma: no cover
+        # This is unreachable because pystac.identify_stac_object raises STACTypeError
+        # for unknown object types before this code is executed
 
     def get_pages(
         self,
diff --git a/tests/test_stac_api_io.py b/tests/test_stac_api_io.py
index 46369a26..948601e1 100644
--- a/tests/test_stac_api_io.py
+++ b/tests/test_stac_api_io.py
@@ -289,3 +289,27 @@ def test_stac_io_in_pystac() -> None:
     stac_io = root._stac_io
     assert isinstance(stac_io, StacApiIO)
     assert stac_io.timeout == 42
+
+
+def test_request_decode_error(requests_mock: Mocker) -> None:
+    """Test that decode errors in request() are properly handled."""
+    url = "https://example.com/bad-encoding"
+    # Mock a response with invalid UTF-8 content
+    requests_mock.get(url, status_code=200, content=b"\xff\xfe\x00\x00")
+
+    stac_api_io = StacApiIO()
+
+    with pytest.raises(APIError) as excinfo:
+        stac_api_io.request(url)
+
+    assert (
+        "decode" in str(excinfo.value).lower() or "utf-8" in str(excinfo.value).lower()
+    )
+
+
+def test_write_text_to_href_url_error() -> None:
+    """Test that write_text_to_href raises APIError for URLs."""
+    stac_api_io = StacApiIO()
+
+    with pytest.raises(APIError, match="Transactions not supported"):
+        stac_api_io.write_text_to_href("https://example.com/write", "content")