diff --git a/.changeset/afraid-ducks-scream.md b/.changeset/afraid-ducks-scream.md
new file mode 100644
index 00000000000..a5fee27c418
--- /dev/null
+++ b/.changeset/afraid-ducks-scream.md
@@ -0,0 +1,5 @@
+---
+'@itwin/itwinui-react': patch
+---
+
+Fixed `ThemeProvider` bug of re-mounting its children and losing state when `portalContainer` is toggled between `undefined` and defined.
diff --git a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Custom Filter.png b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Custom Filter.png
index 643d0002f77..ea4e5c5ca99 100755
Binary files a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Custom Filter.png and b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Custom Filter.png differ
diff --git a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Filters.png b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Filters.png
index d7eb34f1483..820d28226b0 100755
Binary files a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Filters.png and b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Filters.png differ
diff --git a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Localized.png b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Localized.png
index 143e04bb539..edfcc8f4041 100755
Binary files a/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Localized.png and b/apps/react-workshop/cypress-visual-screenshots/baseline/Table.test.ts-Localized.png differ
diff --git a/packages/itwinui-react/src/core/Toast/Toaster.tsx b/packages/itwinui-react/src/core/Toast/Toaster.tsx
index 4f3ba151c75..f33f496a1a9 100644
--- a/packages/itwinui-react/src/core/Toast/Toaster.tsx
+++ b/packages/itwinui-react/src/core/Toast/Toaster.tsx
@@ -104,14 +104,21 @@ export const ToastProvider = ({
     },
   });
 
+  const toasterDispatchContext = React.useContext(ToasterDispatchContext);
+  const toasterStateContext = React.useContext(ToasterStateContext);
+
   // Re-use existing ToastProvider if found
-  if (React.useContext(ToasterStateContext) && inherit) {
-    return children;
-  }
+  const shouldReuse = toasterStateContext && inherit;
+  const toasterDispatchContextValue = shouldReuse
+    ? toasterDispatchContext
+    : dispatch;
+  const toasterStateContextValue = shouldReuse
+    ? toasterStateContext
+    : toasterState;
 
   return (
-    <ToasterDispatchContext.Provider value={dispatch}>
-      <ToasterStateContext.Provider value={toasterState}>
+    <ToasterDispatchContext.Provider value={toasterDispatchContextValue}>
+      <ToasterStateContext.Provider value={toasterStateContextValue}>
         {children}
       </ToasterStateContext.Provider>
     </ToasterDispatchContext.Provider>