diff --git a/.changeset/weak-panthers-fold.md b/.changeset/weak-panthers-fold.md
new file mode 100644
index 00000000..70d24253
--- /dev/null
+++ b/.changeset/weak-panthers-fold.md
@@ -0,0 +1,5 @@
+---
+"@tus/azure-store": patch
+---
+
+Fix error on saving metadata when it contains non-ASCII characters
diff --git a/packages/azure-store/src/index.ts b/packages/azure-store/src/index.ts
index cd41c923..c80ecd5f 100644
--- a/packages/azure-store/src/index.ts
+++ b/packages/azure-store/src/index.ts
@@ -7,6 +7,7 @@ import {
   type KvStore,
   MemoryKvStore,
   TUS_RESUMABLE,
+  Metadata,
 } from '@tus/utils'
 import {
   type AppendBlobClient,
@@ -78,7 +79,11 @@ export class AzureStore extends DataStore {
     await appendBlobClient.setMetadata(
       {
         tus_version: TUS_RESUMABLE,
-        upload: JSON.stringify(upload),
+        upload: JSON.stringify({
+          ...upload,
+          // Base64 encode the metadata to avoid errors for non-ASCII characters
+          metadata: Metadata.stringify(upload.metadata ?? {}),
+        }),
       },
       {}
     )
@@ -110,6 +115,9 @@ export class AzureStore extends DataStore {
       throw ERRORS.FILE_NOT_FOUND
     }
     const upload = JSON.parse(propertyData.metadata.upload) as Upload
+    // Metadata is base64 encoded to avoid errors for non-ASCII characters
+    // so we need to decode it separately
+    upload.metadata = Metadata.parse(JSON.stringify(upload.metadata ?? {}))
 
     await this.cache.set(appendBlobClient.url, upload)
 
diff --git a/test/src/stores.test.ts b/test/src/stores.test.ts
index 5463ca4e..264e55a8 100644
--- a/test/src/stores.test.ts
+++ b/test/src/stores.test.ts
@@ -71,6 +71,18 @@ export const shouldCreateUploads = () => {
       const upload = await this.datastore.getUpload(file.id)
       assert.deepStrictEqual(upload.metadata, file.metadata)
     })
+
+    it('should store `upload_metadata` with non-ASCII characters', async function () {
+      const file = new Upload({
+        id: testId('create-test-non-ascii'),
+        size: 1000,
+        offset: 0,
+        metadata: {filename: '世界_domination_plan.pdf', is_confidential: null},
+      })
+      await this.datastore.create(file)
+      const upload = await this.datastore.getUpload(file.id)
+      assert.deepStrictEqual(upload.metadata, file.metadata)
+    })
   })
 }