diff --git a/pyiceberg/utils/config.py b/pyiceberg/utils/config.py
index ab9b549d25..63120f382d 100644
--- a/pyiceberg/utils/config.py
+++ b/pyiceberg/utils/config.py
@@ -59,10 +59,8 @@ def _lowercase_dictionary_keys(input_dict: RecursiveDict) -> RecursiveDict:
 class Config:
     config: RecursiveDict
 
-    def __init__(self) -> None:
-        config = self._from_configuration_files() or {}
-        config = merge_config(config, self._from_environment_variables(config))
-        self.config = FrozenDict(**config)
+    def __init__(self, config: RecursiveDict | None = None) -> None:
+        self.config = FrozenDict(**(config or {}))
 
     @staticmethod
     def _from_configuration_files() -> RecursiveDict | None:
diff --git a/tests/catalog/test_base.py b/tests/catalog/test_base.py
index 1a47478313..fe1bff583a 100644
--- a/tests/catalog/test_base.py
+++ b/tests/catalog/test_base.py
@@ -16,7 +16,6 @@
 #  under the License.
 # pylint:disable=redefined-outer-name
 
-
 from collections.abc import Generator
 from pathlib import PosixPath
 
diff --git a/tests/catalog/test_bigquery_metastore.py b/tests/catalog/test_bigquery_metastore.py
index c8c7584262..278d342a95 100644
--- a/tests/catalog/test_bigquery_metastore.py
+++ b/tests/catalog/test_bigquery_metastore.py
@@ -14,7 +14,6 @@
 #  KIND, either express or implied.  See the License for the
 #  specific language governing permissions and limitations
 #  under the License.
-import os
 from unittest.mock import MagicMock
 
 from google.api_core.exceptions import NotFound
@@ -25,6 +24,7 @@
 from pyiceberg.catalog.bigquery_metastore import ICEBERG_TABLE_TYPE_VALUE, TABLE_TYPE_PROP, BigQueryMetastoreCatalog
 from pyiceberg.exceptions import NoSuchTableError
 from pyiceberg.schema import Schema
+from pyiceberg.utils.config import Config
 
 
 def dataset_mock() -> Dataset:
@@ -59,7 +59,10 @@ def test_create_table_with_database_location(
 
     mocker.patch("pyiceberg.catalog.bigquery_metastore.Client", return_value=client_mock)
     mocker.patch("pyiceberg.catalog.bigquery_metastore.FromInputFile.table_metadata", return_value=file_mock)
-    mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    mocker.patch(
+        "pyiceberg.catalog.bigquery_metastore.Config",
+        return_value=Config({"legacy-current-snapshot-id": "True"}),
+    )
     mocker.patch("pyiceberg.catalog.ToOutputFile.table_metadata", return_value=None)
 
     catalog_name = "test_ddb_catalog"
@@ -85,7 +88,10 @@ def test_drop_table_with_database_location(
 
     mocker.patch("pyiceberg.catalog.bigquery_metastore.Client", return_value=client_mock)
     mocker.patch("pyiceberg.catalog.bigquery_metastore.FromInputFile.table_metadata", return_value=file_mock)
-    mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    mocker.patch(
+        "pyiceberg.catalog.bigquery_metastore.Config",
+        return_value=Config({"legacy-current-snapshot-id": "True"}),
+    )
     mocker.patch("pyiceberg.catalog.ToOutputFile.table_metadata", return_value=None)
 
     catalog_name = "test_ddb_catalog"
@@ -111,7 +117,10 @@ def test_drop_table_with_database_location(
 def test_drop_namespace(mocker: MockFixture, gcp_dataset_name: str) -> None:
     client_mock = MagicMock()
     mocker.patch("pyiceberg.catalog.bigquery_metastore.Client", return_value=client_mock)
-    mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    mocker.patch(
+        "pyiceberg.catalog.bigquery_metastore.Config",
+        return_value=Config({"legacy-current-snapshot-id": "True"}),
+    )
 
     catalog_name = "test_catalog"
     test_catalog = BigQueryMetastoreCatalog(catalog_name, **{"gcp.bigquery.project-id": "alexstephen-test-1"})
@@ -146,7 +155,10 @@ def test_list_tables(mocker: MockFixture, gcp_dataset_name: str) -> None:
     client_mock.get_table.return_value = table_mock()
 
     mocker.patch("pyiceberg.catalog.bigquery_metastore.Client", return_value=client_mock)
-    mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    mocker.patch(
+        "pyiceberg.catalog.bigquery_metastore.Config",
+        return_value=Config({"legacy-current-snapshot-id": "True"}),
+    )
 
     catalog_name = "test_catalog"
     test_catalog = BigQueryMetastoreCatalog(catalog_name, **{"gcp.bigquery.project-id": "my-project"})
@@ -168,7 +180,10 @@ def test_list_namespaces(mocker: MockFixture) -> None:
     client_mock.list_datasets.return_value = iter([dataset_item_1, dataset_item_2])
 
     mocker.patch("pyiceberg.catalog.bigquery_metastore.Client", return_value=client_mock)
-    mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    mocker.patch(
+        "pyiceberg.catalog.bigquery_metastore.Config",
+        return_value=Config({"legacy-current-snapshot-id": "True"}),
+    )
 
     catalog_name = "test_catalog"
     test_catalog = BigQueryMetastoreCatalog(catalog_name, **{"gcp.bigquery.project-id": "my-project"})
diff --git a/tests/catalog/test_rest.py b/tests/catalog/test_rest.py
index 99d1ef947b..d6583fd407 100644
--- a/tests/catalog/test_rest.py
+++ b/tests/catalog/test_rest.py
@@ -2036,18 +2036,18 @@ def test_catalog_from_environment_variables(catalog_config_mock: mock.Mock, rest
 
 
 @mock.patch.dict(os.environ, EXAMPLE_ENV)
-@mock.patch("pyiceberg.catalog._ENV_CONFIG.get_catalog_config")
-def test_catalog_from_environment_variables_override(catalog_config_mock: mock.Mock, rest_mock: Mocker) -> None:
+def test_catalog_from_environment_variables_override(rest_mock: Mocker) -> None:
     rest_mock.get(
         "https://other-service.io/api/v1/config",
         json={"defaults": {}, "overrides": {}},
         status_code=200,
     )
     env_config: RecursiveDict = Config._from_environment_variables({})
-
-    catalog_config_mock.return_value = cast(RecursiveDict, env_config.get("catalog")).get("production")
-    catalog = cast(RestCatalog, load_catalog("production", uri="https://other-service.io/api"))
-    assert catalog.uri == "https://other-service.io/api"
+    mock_env_config = mock.Mock()
+    mock_env_config.get_catalog_config.return_value = cast(RecursiveDict, env_config.get("catalog")).get("production")
+    with mock.patch("pyiceberg.catalog._ENV_CONFIG", mock_env_config):
+        catalog = cast(RestCatalog, load_catalog("production", uri="https://other-service.io/api"))
+        assert catalog.uri == "https://other-service.io/api"
 
 
 def test_catalog_from_parameters_empty_env(rest_mock: Mocker) -> None:
diff --git a/tests/test_serializers.py b/tests/test_serializers.py
index 53ce6fcd42..eaa2d1bcbb 100644
--- a/tests/test_serializers.py
+++ b/tests/test_serializers.py
@@ -28,6 +28,7 @@
 from pyiceberg.table.metadata import TableMetadataV1
 from pyiceberg.table.update import AssertRefSnapshotId, TableRequirement
 from pyiceberg.typedef import IcebergBaseModel
+from pyiceberg.utils.config import Config
 
 
 def test_legacy_current_snapshot_id(
@@ -42,6 +43,15 @@ def test_legacy_current_snapshot_id(
     assert static_table.metadata.current_snapshot_id is None
 
     mocker.patch.dict(os.environ, values={"PYICEBERG_LEGACY_CURRENT_SNAPSHOT_ID": "True"})
+    env_config = Config._from_environment_variables({})
+    mocker.patch(
+        "pyiceberg.serializers.Config",
+        return_value=Config(env_config),
+    )
+    mocker.patch(
+        "pyiceberg.table.metadata.Config",
+        return_value=Config(env_config),
+    )
 
     ToOutputFile.table_metadata(metadata, PyArrowFileIO().new_output(location=metadata_location), overwrite=True)
     with PyArrowFileIO().new_input(location=metadata_location).open() as input_stream:
diff --git a/tests/utils/test_config.py b/tests/utils/test_config.py
index 5cd6a7203a..21434c9ec8 100644
--- a/tests/utils/test_config.py
+++ b/tests/utils/test_config.py
@@ -28,8 +28,20 @@
 
 
 def test_config() -> None:
-    """To check if all the file lookups go well without any mocking"""
+    """Config() should be a pure empty container and perform no implicit IO."""
     assert Config()
+    assert Config().config == {}
+
+
+def test_config_does_not_load_implicitly() -> None:
+    with (
+        mock.patch.object(Config, "_from_configuration_files") as from_files_mock,
+        mock.patch.object(Config, "_from_environment_variables") as from_env_mock,
+    ):
+        Config()
+
+    from_files_mock.assert_not_called()
+    from_env_mock.assert_not_called()
 
 
 @mock.patch.dict(os.environ, EXAMPLE_ENV)
@@ -183,3 +195,14 @@ def create_config_file(path: str, uri: str | None) -> None:
     assert (
         result["catalog"]["default"]["uri"] if result else None  # type: ignore
     ) == expected_result, f"Unexpected configuration result. Expected: {expected_result}, Actual: {result}"
+
+
+def test_load_reads_file_and_environment_once(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv("PYICEBERG_CATALOG__PRODUCTION__URI", "https://env.service.io/api")
+    with mock.patch.object(
+        Config, "_from_configuration_files", return_value={"catalog": {"production": {"type": "rest"}}}
+    ) as files_mock:
+        config = Config()
+
+    files_mock.assert_called_once()
+    assert config.get_catalog_config("production") == {"type": "rest", "uri": "https://env.service.io/api"}