diff --git a/src/core/public/overlays/sidecar/__snapshots__/sidecar_service.test.tsx.snap b/src/core/public/overlays/sidecar/__snapshots__/sidecar_service.test.tsx.snap
index 16b97237b7c7..f183bb4cccb4 100644
--- a/src/core/public/overlays/sidecar/__snapshots__/sidecar_service.test.tsx.snap
+++ b/src/core/public/overlays/sidecar/__snapshots__/sidecar_service.test.tsx.snap
@@ -12,6 +12,8 @@ Array [
 ]
 `;
 
+exports[`SidecarService open sidecar does not unmount if targetDom is null 1`] = `"<div class=\\"osdSidecarFlyout osdSidecarFlyout--dockedRight\\" style=\\"width: 460px;\\"><button class=\\"resizableButton resizableButton--horizontal\\" data-test-subj=\\"resizableButton\\" type=\\"button\\"></button><div class=\\"osdSidecarMountWrapper\\"><span>Sidecar content</span></div></div>"`;
+
 exports[`SidecarService open sidecar renders a sidecar to the DOM 1`] = `"<div class=\\"osdSidecarFlyout osdSidecarFlyout--dockedRight\\" style=\\"width: 460px;\\"><button class=\\"resizableButton resizableButton--horizontal\\" data-test-subj=\\"resizableButton\\" type=\\"button\\"></button><div class=\\"osdSidecarMountWrapper\\"><span>Sidecar content</span></div></div>"`;
 
 exports[`SidecarService open sidecar with a currently active sidecar replaces the current sidecar with a new one 1`] = `"<div class=\\"osdSidecarFlyout osdSidecarFlyout--dockedRight\\" style=\\"width: 460px;\\"><button class=\\"resizableButton resizableButton--horizontal\\" data-test-subj=\\"resizableButton\\" type=\\"button\\"></button><div class=\\"osdSidecarMountWrapper\\"><span>Sidecar content 2</span></div></div>"`;
diff --git a/src/core/public/overlays/sidecar/components/__snapshots__/resizable_button.test.tsx.snap b/src/core/public/overlays/sidecar/components/__snapshots__/resizable_button.test.tsx.snap
index 9d46091330c3..8acfbacadd5c 100644
--- a/src/core/public/overlays/sidecar/components/__snapshots__/resizable_button.test.tsx.snap
+++ b/src/core/public/overlays/sidecar/components/__snapshots__/resizable_button.test.tsx.snap
@@ -44,7 +44,18 @@ exports[`it should emit onResize with min size when drag if new size is below th
 />
 `;
 
-exports[`it should emit onResize with new flyout size when drag and horizontal 1`] = `
+exports[`it should emit onResize with new flyout size when docked left and drag and horizontal 1`] = `
+<button
+  className="resizableButton resizableButton--horizontal"
+  data-test-subj="resizableButton"
+  onClick={[Function]}
+  onMouseDown={[Function]}
+  onTouchStart={[Function]}
+  type="button"
+/>
+`;
+
+exports[`it should emit onResize with new flyout size when docked right and drag and horizontal 1`] = `
 <button
   className="resizableButton resizableButton--horizontal"
   data-test-subj="resizableButton"
diff --git a/src/core/public/overlays/sidecar/components/resizable_button.test.tsx b/src/core/public/overlays/sidecar/components/resizable_button.test.tsx
index addd81e4aa9a..c388c3cffd46 100644
--- a/src/core/public/overlays/sidecar/components/resizable_button.test.tsx
+++ b/src/core/public/overlays/sidecar/components/resizable_button.test.tsx
@@ -44,7 +44,7 @@ test('it should be vertical when docked mode is takeover', () => {
   expect(component).toMatchSnapshot();
 });
 
-test('it should emit onResize with new flyout size when drag and horizontal', () => {
+test('it should emit onResize with new flyout size when docked right and drag and horizontal', () => {
   const windowEvents = storeWindowEvents();
 
   const onResize = jest.fn();
@@ -60,6 +60,22 @@ test('it should emit onResize with new flyout size when drag and horizontal', ()
   expect(component).toMatchSnapshot();
 });
 
+test('it should emit onResize with new flyout size when docked left and drag and horizontal', () => {
+  const windowEvents = storeWindowEvents();
+
+  const onResize = jest.fn();
+  const newProps = { ...props, onResize, dockedMode: SIDECAR_DOCKED_MODE.LEFT };
+  const component = shallow(<ResizableButton {...newProps} />);
+  const resizer = component.find(`[data-test-subj~="resizableButton"]`).first();
+  expect(onResize).not.toHaveBeenCalled();
+  resizer.simulate('mousedown', { clientX: 0, pageX: 0, pageY: 0 });
+  windowEvents?.mousemove({ clientX: 1000, pageX: 0, pageY: 0 });
+  windowEvents?.mouseup();
+  const newSize = 1000 + DEFAULT_FLYOUT_SIZE;
+  expect(onResize).toHaveBeenCalledWith(newSize);
+  expect(component).toMatchSnapshot();
+});
+
 test('it should emit onResize with new flyout size when drag and vertical', () => {
   const windowEvents = storeWindowEvents();
 
diff --git a/src/core/public/overlays/sidecar/sidecar_service.test.tsx b/src/core/public/overlays/sidecar/sidecar_service.test.tsx
index b9f10912b97d..b1b2d57aa641 100644
--- a/src/core/public/overlays/sidecar/sidecar_service.test.tsx
+++ b/src/core/public/overlays/sidecar/sidecar_service.test.tsx
@@ -53,6 +53,16 @@ describe('SidecarService', () => {
       const content = mount(mockReactDomRender.mock.calls[0][0]);
       expect(content.html()).toMatchSnapshot();
     });
+
+    it('does not unmount if targetDom is null', async () => {
+      const sidecarRef = new SidecarService().start({ i18n: i18nMock, targetDomElement: null });
+      const ref = sidecarRef.open(mountText('Sidecar content'), options);
+      const content = mount(mockReactDomRender.mock.calls[0][0]);
+      expect(content.html()).toMatchSnapshot();
+      await ref.close();
+      expect(mockReactDomUnmount).not.toHaveBeenCalled();
+    });
+
     describe('with a currently active sidecar', () => {
       let ref1: OverlayRef;
       beforeEach(() => {
diff --git a/src/core/public/overlays/sidecar/sidecar_service.tsx b/src/core/public/overlays/sidecar/sidecar_service.tsx
index adbd0d327a92..7612410d475a 100644
--- a/src/core/public/overlays/sidecar/sidecar_service.tsx
+++ b/src/core/public/overlays/sidecar/sidecar_service.tsx
@@ -102,7 +102,7 @@ export interface OverlaySidecarOpenOptions {
 
 interface StartDeps {
   i18n: I18nStart;
-  targetDomElement: Element;
+  targetDomElement: Element | null;
 }
 
 export enum SIDECAR_DOCKED_MODE {