diff --git a/packages/frontend/src/lib/server/user/index.ts b/packages/frontend/src/lib/server/user/index.ts
index f4df357..0ae39e6 100644
--- a/packages/frontend/src/lib/server/user/index.ts
+++ b/packages/frontend/src/lib/server/user/index.ts
@@ -1 +1,2 @@
 export { update } from "./update";
+export { uploadAvatar } from "./uploadAvatar";
diff --git a/packages/frontend/src/lib/server/user/uploadAvatar.ts b/packages/frontend/src/lib/server/user/uploadAvatar.ts
new file mode 100644
index 0000000..c9e278c
--- /dev/null
+++ b/packages/frontend/src/lib/server/user/uploadAvatar.ts
@@ -0,0 +1,54 @@
+import { getAuthHeaders, getServerURL, resizeImageToSquare } from "@/lib/utils";
+import type { ServerQueryInput } from "..";
+
+export async function uploadAvatar({
+    file,
+    onSuccess,
+    onError,
+}: {
+    file: File;
+} & ServerQueryInput) {
+    const MAX_FILE_SIZE = 5 * 1024 * 1024;
+    const ALLOWED_TYPES = ["image/png", "image/jpeg", "image/webp", "image/gif"];
+
+    if (file.size > MAX_FILE_SIZE) {
+        onError?.("File size exceeds 5MB limit");
+        return;
+    }
+
+    if (!ALLOWED_TYPES.includes(file.type)) {
+        onError?.("Invalid file type. Allowed types: png, jpg, jpeg, webp, gif");
+        return;
+    }
+
+    let resizedFile: File;
+    try {
+        const blob = await resizeImageToSquare(file, 256);
+        resizedFile = new File([blob], "avatar.png", { type: "image/png" });
+    } catch (_error) {
+        onError?.("Failed to resize image");
+        return;
+    }
+
+    const formData = new FormData();
+    formData.append("file", resizedFile);
+
+    const res = await fetch(`${getServerURL()}/user/upload-avatar`, {
+        method: "POST",
+        headers: getAuthHeaders(),
+        body: formData,
+    });
+
+    if (!res.ok) {
+        const error = await res.text();
+        onError?.(error || `Failed to upload avatar (${res.status})`);
+        return;
+    }
+
+    const data = await res.json();
+    if (data.avatarURL) {
+        onSuccess?.(data.avatarURL, res);
+    } else {
+        onError?.("Failed to upload avatar");
+    }
+}