diff --git a/frontend/src/core/uploads/api.ts b/frontend/src/core/uploads/api.ts
index e70279061..a12688685 100644
--- a/frontend/src/core/uploads/api.ts
+++ b/frontend/src/core/uploads/api.ts
@@ -116,8 +116,9 @@ export async function deleteUploadedFile(
   threadId: string,
   filename: string,
 ): Promise<{ success: boolean; message: string }> {
+  const encodedFilename = encodeURIComponent(filename);
   const response = await fetch(
-    `${getBackendBaseURL()}/api/threads/${threadId}/uploads/${filename}`,
+    `${getBackendBaseURL()}/api/threads/${threadId}/uploads/${encodedFilename}`,
     {
       method: "DELETE",
     },
diff --git a/frontend/tests/unit/core/uploads/api.test.ts b/frontend/tests/unit/core/uploads/api.test.ts
new file mode 100644
index 000000000..3cdb83a4e
--- /dev/null
+++ b/frontend/tests/unit/core/uploads/api.test.ts
@@ -0,0 +1,49 @@
+import { beforeEach, describe, expect, rs, test } from "@rstest/core";
+
+rs.mock("@/core/api/fetcher", () => ({
+  fetch: rs.fn(),
+}));
+
+rs.mock("@/core/config", () => ({
+  getBackendBaseURL: () => "/backend",
+}));
+
+import { fetch as fetcher } from "@/core/api/fetcher";
+import { deleteUploadedFile } from "@/core/uploads/api";
+
+const mockedFetch = rs.mocked(fetcher);
+
+function jsonResponse(status: number, body: unknown): Response {
+  return new Response(JSON.stringify(body), {
+    status,
+    statusText: status >= 400 ? "Error" : "OK",
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+beforeEach(() => {
+  mockedFetch.mockReset();
+});
+
+describe("uploads api", () => {
+  test("encodes uploaded filenames in delete request paths", async () => {
+    mockedFetch.mockResolvedValueOnce(
+      jsonResponse(200, {
+        success: true,
+        message: "Deleted report#1?.txt",
+      }),
+    );
+
+    await expect(
+      deleteUploadedFile("thread-1", "report#1?.txt"),
+    ).resolves.toEqual({
+      success: true,
+      message: "Deleted report#1?.txt",
+    });
+
+    expect(mockedFetch).toHaveBeenCalledWith(
+      "/backend/api/threads/thread-1/uploads/report%231%3F.txt",
+      { method: "DELETE" },
+    );
+  });
+});