diff --git a/src/TreeDataGrid.tsx b/src/TreeDataGrid.tsx
index 2de102da6d..7aea6211aa 100644
--- a/src/TreeDataGrid.tsx
+++ b/src/TreeDataGrid.tsx
@@ -36,6 +36,7 @@ export interface TreeDataGridProps<R, SR = unknown, K extends Key = Key>
   ) => Record<string, readonly NoInfer<R>[]>;
   expandedGroupIds: ReadonlySet<unknown>;
   onExpandedGroupIdsChange: (expandedGroupIds: Set<unknown>) => void;
+  generateGroupId?: (groupKey: string, parentId?: string) => string;
 }
 
 type GroupByDictionary<TRow> = Record<
@@ -62,6 +63,7 @@ function TreeDataGrid<R, SR, K extends Key>(
     rowGrouper,
     expandedGroupIds,
     onExpandedGroupIdsChange,
+    generateGroupId,
     ...props
   }: TreeDataGridProps<R, SR, K>,
   ref: React.Ref<DataGridHandle>
@@ -144,6 +146,15 @@ function TreeDataGrid<R, SR, K extends Key>(
     if (!groupedRows) return [rawRows, isGroupRow];
 
     const flattenedRows: Array<R | GroupRow<R>> = [];
+
+    const groupIdGenerator = (groupKey: string, parentId?: string) => {
+      if (generateGroupId !== undefined && typeof generateGroupId === 'function') {
+        return generateGroupId(groupKey, parentId);
+      }
+
+      return `${parentId}__${groupKey}`;
+    };
+
     const expandGroup = (
       rows: GroupByDictionary<R> | readonly R[],
       parentId: string | undefined,
@@ -154,8 +165,7 @@ function TreeDataGrid<R, SR, K extends Key>(
         return;
       }
       Object.keys(rows).forEach((groupKey, posInSet, keys) => {
-        // TODO: should users have control over the generated key?
-        const id = parentId !== undefined ? `${parentId}__${groupKey}` : groupKey;
+        const id = groupIdGenerator(groupKey, parentId);
         const isExpanded = expandedGroupIds.has(id);
         const { childRows, childGroups, startRowIndex } = rows[groupKey];
 
@@ -185,7 +195,7 @@ function TreeDataGrid<R, SR, K extends Key>(
     function isGroupRow(row: R | GroupRow<R>): row is GroupRow<R> {
       return allGroupRows.has(row);
     }
-  }, [expandedGroupIds, groupedRows, rawRows]);
+  }, [expandedGroupIds, groupedRows, rawRows, generateGroupId]);
 
   const rowHeight = useMemo(() => {
     if (typeof rawRowHeight === 'function') {
diff --git a/test/TreeDataGrid.test.tsx b/test/TreeDataGrid.test.tsx
index 1f252bf5db..0f55399445 100644
--- a/test/TreeDataGrid.test.tsx
+++ b/test/TreeDataGrid.test.tsx
@@ -93,7 +93,12 @@ function rowKeyGetter(row: Row) {
   return row.id;
 }
 
-function TestGrid({ groupBy }: { groupBy: string[] }) {
+interface TestGridProps {
+  groupBy: string[];
+  generateGroupId: ((groupKey: string, parentId?: string) => string) | undefined;
+}
+
+function TestGrid({ groupBy, generateGroupId }: TestGridProps) {
   const [rows, setRows] = useState(initialRows);
   const [selectedRows, setSelectedRows] = useState((): ReadonlySet<number> => new Set());
   const [expandedGroupIds, setExpandedGroupIds] = useState(
@@ -122,12 +127,16 @@ function TestGrid({ groupBy }: { groupBy: string[] }) {
       onExpandedGroupIdsChange={setExpandedGroupIds}
       onRowsChange={setRows}
       onPaste={onPaste}
+      {...(generateGroupId && { generateGroupId })}
     />
   );
 }
 
-function setup(groupBy: string[]) {
-  render(<TestGrid groupBy={groupBy} />);
+function setup(
+  groupBy: string[],
+  generateGroupId?: (groupKey: string, parentId?: string) => string
+) {
+  render(<TestGrid groupBy={groupBy} generateGroupId={generateGroupId} />);
 }
 
 function getHeaderCellsContent() {
@@ -161,6 +170,15 @@ test('should group by multiple columns', () => {
   expect(getRows()).toHaveLength(4);
 });
 
+test('should group by multiple columns when passing generateGroupId', () => {
+  setup(['country', 'year'], (groupKey, parentId) =>
+    parentId !== undefined ? `${groupKey}#${parentId}` : groupKey
+  );
+  expect(getTreeGrid()).toHaveAttribute('aria-rowcount', '13');
+  expect(getHeaderCellsContent()).toStrictEqual(['', 'Country', 'Year', 'Sport', 'Id']);
+  expect(getRows()).toHaveLength(4);
+});
+
 test('should ignore duplicate groupBy columns', () => {
   setup(['year', 'year', 'year']);
   expect(getTreeGrid()).toHaveAttribute('aria-rowcount', '10');
@@ -184,6 +202,20 @@ test('should toggle group when group cell is clicked', async () => {
   expect(getRows()).toHaveLength(5);
 });
 
+test('should toggle group when group cell is clicked and is passing `generateGroupId` props', async () => {
+  setup(['country', 'year'], (groupKey, parentId) =>
+    parentId !== undefined ? `${groupKey}#${parentId}` : groupKey
+  );
+  expect(getTreeGrid()).toHaveAttribute('aria-rowcount', '13');
+  expect(getHeaderCellsContent()).toStrictEqual(['', 'Country', 'Year', 'Sport', 'Id']);
+  await userEvent.click(screen.getByRole('gridcell', { name: 'USA' }));
+  expect(getRows()).toHaveLength(6);
+  await userEvent.click(screen.getByRole('gridcell', { name: 'Canada' }));
+  expect(getRows()).toHaveLength(8);
+  await userEvent.click(screen.getByRole('gridcell', { name: '2020' }));
+  expect(getRows()).toHaveLength(9);
+});
+
 test('should toggle group using keyboard', async () => {
   setup(['year']);
   expect(getRows()).toHaveLength(5);