diff --git a/change/@griffel-core-69be5d24-4050-4443-a10d-75722b29e744.json b/change/@griffel-core-69be5d24-4050-4443-a10d-75722b29e744.json
new file mode 100644
index 0000000000..38738b4dcc
--- /dev/null
+++ b/change/@griffel-core-69be5d24-4050-4443-a10d-75722b29e744.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: handle empty strings in mergeClasses()",
+  "packageName": "@griffel/core",
+  "email": "olfedias@microsoft.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/core/src/mergeClasses.test.ts b/packages/core/src/mergeClasses.test.ts
index 876d29c85b..47d5aff474 100644
--- a/packages/core/src/mergeClasses.test.ts
+++ b/packages/core/src/mergeClasses.test.ts
@@ -52,6 +52,11 @@ describe('mergeClasses', () => {
     expect(mergeClasses(undefined, false)).toBe('');
   });
 
+  it('handles empty classes', () => {
+    expect(mergeClasses('ui-button', '', 'ui-toogle-button')).toBe('ui-button ui-toogle-button');
+    expect(mergeClasses('', '')).toBe('');
+  });
+
   it('performs deduplication for multiple arguments', () => {
     const classes = makeStyles({
       block: { display: 'block' },
diff --git a/packages/core/src/mergeClasses.ts b/packages/core/src/mergeClasses.ts
index 3cf7a6e26e..d780977750 100644
--- a/packages/core/src/mergeClasses.ts
+++ b/packages/core/src/mergeClasses.ts
@@ -46,7 +46,7 @@ export function mergeClasses(): string {
   for (let i = 0; i < arguments.length; i++) {
     const className = arguments[i];
 
-    if (typeof className === 'string') {
+    if (typeof className === 'string' && className !== '') {
       // All classes generated by `makeStyles()` are prefixed by a sequence hash, this allows to identify class sets
       // without parsing each className in a string
       const sequenceIndex = className.indexOf(SEQUENCE_PREFIX);