diff --git a/plugins/catalog-react/src/components/EntityNamespacePicker/EntityNamespacePicker.test.tsx b/plugins/catalog-react/src/components/EntityNamespacePicker/EntityNamespacePicker.test.tsx
new file mode 100644
index 0000000000..12acdc9f46
--- /dev/null
+++ b/plugins/catalog-react/src/components/EntityNamespacePicker/EntityNamespacePicker.test.tsx
@@ -0,0 +1,234 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Entity } from '@backstage/catalog-model';
+import { fireEvent, render, screen } from '@testing-library/react';
+import React from 'react';
+import { MockEntityListContextProvider } from '../../testUtils/providers';
+import { EntityNamespaceFilter } from '../../filters';
+import { EntityNamespacePicker } from './EntityNamespacePicker';
+
+const sampleEntities: Entity[] = [
+  {
+    apiVersion: '1',
+    kind: 'Component',
+    metadata: {
+      name: 'component-1',
+      namespace: 'namespace-1',
+    },
+    spec: {
+      lifecycle: 'production',
+    },
+  },
+  {
+    apiVersion: '1',
+    kind: 'Component',
+    metadata: {
+      name: 'component-2',
+      namespace: 'namespace-2',
+    },
+    spec: {
+      lifecycle: 'experimental',
+    },
+  },
+  {
+    apiVersion: '1',
+    kind: 'Component',
+    metadata: {
+      name: 'component-3',
+      namespace: 'namespace-3',
+    },
+    spec: {
+      lifecycle: 'experimental',
+    },
+  },
+];
+
+describe('<EntityNamespacePicker/>', () => {
+  it('renders all namespaces', () => {
+    render(
+      <MockEntityListContextProvider
+        value={{ entities: sampleEntities, backendEntities: sampleEntities }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(screen.getByText('Namespace')).toBeInTheDocument();
+
+    fireEvent.click(screen.getByTestId('namespace-picker-expand'));
+    sampleEntities
+      .map(e => e.metadata.namespace!)
+      .forEach(namespace => {
+        expect(screen.getByText(namespace as string)).toBeInTheDocument();
+      });
+  });
+
+  it('renders unique namespaces in alphabetical order', () => {
+    render(
+      <MockEntityListContextProvider
+        value={{ entities: sampleEntities, backendEntities: sampleEntities }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(screen.getByText('Namespace')).toBeInTheDocument();
+
+    fireEvent.click(screen.getByTestId('namespace-picker-expand'));
+
+    expect(screen.getAllByRole('option').map(o => o.textContent)).toEqual([
+      'namespace-1',
+      'namespace-2',
+      'namespace-3',
+    ]);
+  });
+
+  it('respects the query parameter filter value', () => {
+    const updateFilters = jest.fn();
+    const queryParameters = { namespace: ['namespace-1'] };
+    render(
+      <MockEntityListContextProvider
+        value={{
+          entities: sampleEntities,
+          backendEntities: sampleEntities,
+          updateFilters,
+          queryParameters,
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-1']),
+    });
+  });
+
+  it('adds namespaces to filters', () => {
+    const updateFilters = jest.fn();
+    render(
+      <MockEntityListContextProvider
+        value={{
+          entities: sampleEntities,
+          backendEntities: sampleEntities,
+          updateFilters,
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: undefined,
+    });
+
+    fireEvent.click(screen.getByTestId('namespace-picker-expand'));
+    fireEvent.click(screen.getByText('namespace-2'));
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-2']),
+    });
+  });
+
+  it('removes namespaces from filters', () => {
+    const updateFilters = jest.fn();
+    render(
+      <MockEntityListContextProvider
+        value={{
+          entities: sampleEntities,
+          backendEntities: sampleEntities,
+          updateFilters,
+          filters: { namespace: new EntityNamespaceFilter(['namespace-2']) },
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-2']),
+    });
+    fireEvent.click(screen.getByTestId('namespace-picker-expand'));
+    expect(screen.getByLabelText('namespace-2')).toBeChecked();
+
+    fireEvent.click(screen.getByLabelText('namespace-2'));
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: undefined,
+    });
+  });
+
+  it('responds to external queryParameters changes', () => {
+    const updateFilters = jest.fn();
+    const rendered = render(
+      <MockEntityListContextProvider
+        value={{
+          updateFilters,
+          queryParameters: { namespace: ['namespace-1'] },
+          backendEntities: sampleEntities,
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-1']),
+    });
+    rendered.rerender(
+      <MockEntityListContextProvider
+        value={{
+          updateFilters,
+          queryParameters: { namespace: ['namespace-2'] },
+          backendEntities: sampleEntities,
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-2']),
+    });
+  });
+  it('removes namespaces from filters if there are no available namespaces', () => {
+    const updateFilters = jest.fn();
+    render(
+      <MockEntityListContextProvider
+        value={{
+          updateFilters,
+          queryParameters: { namespace: ['namespace-1'] },
+          backendEntities: [],
+        }}
+      >
+        <EntityNamespacePicker />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: undefined,
+    });
+  });
+  it('responds to initialFilter prop', () => {
+    const updateFilters = jest.fn();
+    render(
+      <MockEntityListContextProvider
+        value={{
+          entities: sampleEntities,
+          backendEntities: sampleEntities,
+          updateFilters,
+        }}
+      >
+        <EntityNamespacePicker initialFilter={['namespace-2']} />
+      </MockEntityListContextProvider>,
+    );
+    expect(updateFilters).toHaveBeenLastCalledWith({
+      namespace: new EntityNamespaceFilter(['namespace-2']),
+    });
+  });
+});
diff --git a/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx b/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
index f8a655413e..c80b340349 100644
--- a/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
+++ b/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
@@ -186,6 +186,7 @@ describe('CatalogTable component', () => {
         'Owner',
         'Type',
         'Lifecycle',
+        'Namespace',
         'Description',
         'Tags',
         'Actions',
@@ -199,6 +200,7 @@ describe('CatalogTable component', () => {
         'Owner',
         'Type',
         'Lifecycle',
+        'Namespace',
         'Description',
         'Tags',
         'Actions',
@@ -231,6 +233,7 @@ describe('CatalogTable component', () => {
         'Owner',
         'Type',
         'Lifecycle',
+        'Namespace',
         'Description',
         'Tags',
         'Actions',
@@ -256,6 +259,7 @@ describe('CatalogTable component', () => {
         'Owner',
         'Type',
         'Lifecycle',
+        'Namespace',
         'Description',
         'Tags',
         'Actions',
@@ -269,6 +273,7 @@ describe('CatalogTable component', () => {
         'Owner',
         'Type',
         'Lifecycle',
+        'Namespace',
         'Description',
         'Tags',
         'Actions',