diff --git a/frontend/app/lib/actions.ts b/frontend/app/lib/actions.ts
index 88d9a3d4..f7b4fb69 100644
--- a/frontend/app/lib/actions.ts
+++ b/frontend/app/lib/actions.ts
@@ -884,3 +884,10 @@ export async function createUserWithOauth(
     redirect("/login");
   }
 }
+
+export const isOnline = async (userId: number) =>
+  fetch(`${process.env.API_URL}/chat/${userId}/online`, {
+    headers: {
+      Authorization: "Bearer " + getAccessToken(),
+    },
+  }).then((res) => (res.ok ? res.json() : Promise.reject(res)));
diff --git a/frontend/app/pong/GameCard.tsx b/frontend/app/pong/GameCard.tsx
index 74f111ae..242cf7d4 100644
--- a/frontend/app/pong/GameCard.tsx
+++ b/frontend/app/pong/GameCard.tsx
@@ -1,18 +1,24 @@
 "use client";
 
+import { Avatar } from "@/app/ui/user/avatar";
 import { Button } from "@/components/ui/button";
 import { Card } from "@/components/ui/card";
 import { TooltipProvider } from "@radix-ui/react-tooltip";
 import { useRouter } from "next/navigation";
 import { PublicUserEntity } from "../lib/dtos";
-import UserTooltip from "../ui/user/user-tool-tip";
 
 function UserCard({ user }: { user: PublicUserEntity }) {
   return (
     <>
       <div className="flex gap-4 items-center">
         {user.name}
-        <UserTooltip user={user} avatarSize="medium" />
+        <Avatar
+          avatarURL={user.avatarURL}
+          size="medium"
+          href={`/user/${user.id}`}
+          alt={user.name}
+          online={true}
+        />
       </div>
     </>
   );
diff --git a/frontend/app/room/[id]/sidebar-item.tsx b/frontend/app/room/[id]/sidebar-item.tsx
index 9f4c93e7..2b7c97c9 100644
--- a/frontend/app/room/[id]/sidebar-item.tsx
+++ b/frontend/app/room/[id]/sidebar-item.tsx
@@ -13,7 +13,7 @@ import type {
   RoomEntity,
   UserOnRoomEntity,
 } from "@/app/lib/dtos";
-import { SmallAvatarSkeleton } from "@/app/ui/room/skeleton";
+import { Avatar } from "@/app/ui/user/avatar";
 import {
   ContextMenu,
   ContextMenuContent,
@@ -38,13 +38,6 @@ function truncateString(str: string | undefined, num: number): string {
   return str.slice(0, num) + "...";
 }
 
-function Avatar({ avatarURL }: { avatarURL?: string }) {
-  if (!avatarURL) {
-    return <SmallAvatarSkeleton />;
-  }
-  return <img className="rounded-full w-6 h-6 object-cover" src={avatarURL} />;
-}
-
 export interface LeaveEvent {
   userId: number;
   roomId: number;
@@ -141,7 +134,7 @@ export default function SidebarItem({
       {!isKicked && (
         <ContextMenu>
           <ContextMenuTrigger className="flex gap-2 items-center group hover:opacity-60">
-            <Avatar avatarURL={user.user.avatarURL} />
+            <Avatar avatarURL={user.user.avatarURL} size="small" />
             <span className="text-muted-foreground text-sm whitespace-nowrap group-hover:text-primary">
               {truncateString(user.user.name, 15)}
               {room.accessLevel !== "DIRECT" && isUserOwner && " 👑"}
diff --git a/frontend/app/ui/room/message-item.tsx b/frontend/app/ui/room/message-item.tsx
index 259f3701..a379f7d4 100644
--- a/frontend/app/ui/room/message-item.tsx
+++ b/frontend/app/ui/room/message-item.tsx
@@ -2,7 +2,6 @@ import type { MessageEvent } from "@/app/lib/dtos";
 import { Avatar } from "@/app/ui/user/avatar";
 import { Stack } from "@/components/layout/stack";
 import { TooltipProvider } from "@radix-ui/react-tooltip";
-import UserTooltip from "../user/user-tool-tip";
 
 export function MessageItem({
   message,
@@ -18,7 +17,11 @@ export function MessageItem({
       {/* Left Side */}
       {withAvatar && (
         <TooltipProvider>
-          <UserTooltip user={message.user} avatarSize="medium"></UserTooltip>
+          <Avatar
+            avatarURL={message.user.avatarURL}
+            size="medium"
+            href={`/user/${message.user.id}`}
+          ></Avatar>
         </TooltipProvider>
       )}
       {!withAvatar && (
diff --git a/frontend/app/ui/user/avatar.tsx b/frontend/app/ui/user/avatar.tsx
index 2e9e99e3..2e71db43 100644
--- a/frontend/app/ui/user/avatar.tsx
+++ b/frontend/app/ui/user/avatar.tsx
@@ -1,40 +1,78 @@
 import { Skeleton } from "@/components/ui/skeleton";
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipProvider,
+  TooltipTrigger,
+} from "@/components/ui/tooltip";
+import Link from "next/link";
 
 export type AvatarSize = "small" | "medium" | "large";
 
-export function Avatar({
-  avatarURL,
-  size,
-  alt,
-}: {
+export interface Props {
   avatarURL?: string;
   size: AvatarSize;
+  href?: string;
   alt?: string;
-}) {
+  online?: boolean;
+}
+
+export function Avatar({ avatarURL, size, href, alt, online }: Props) {
   let sizeClass = "";
+  let onlineStatusClass = online ? "bg-green-500 " : "bg-gray-500 ";
   switch (size) {
     case "small":
       sizeClass = "h-6 w-6";
+      onlineStatusClass += "w-3 h-3 border-2";
       break;
     case "medium":
       sizeClass = "h-10 w-10";
+      onlineStatusClass += "w-4 h-4 border-2";
       break;
     case "large":
-      sizeClass = "h-32 w-32";
+      sizeClass = "h-28 w-28";
+      onlineStatusClass += "w-8 h-8 border-4";
       break;
     default:
-      sizeClass = "h-10 w-10";
-      break;
+      throw new Error("Invalid size");
   }
   if (!avatarURL) {
     return <Skeleton className={`flex-none rounded-full ${sizeClass}`} />;
-  } else {
-    return (
-      <img
-        className={`flex-none rounded-full object-cover ${sizeClass}`}
-        src={avatarURL}
-        alt={alt}
-      />
-    );
   }
+  const TooltipWrapper = ({ children }: { children: React.ReactNode }) =>
+    alt !== undefined ? (
+      <Tooltip>
+        <TooltipTrigger asChild>{children}</TooltipTrigger>
+        <TooltipContent>{alt}</TooltipContent>
+      </Tooltip>
+    ) : (
+      children
+    );
+  const LinkWrapper = ({ children }: { children: React.ReactNode }) =>
+    href !== undefined ? <Link href={href}>{children}</Link> : children;
+  return (
+    <LinkWrapper>
+      <div className={`relative flex-none ${sizeClass}`}>
+        <TooltipProvider delayDuration={0}>
+          <TooltipWrapper>
+            <img
+              className={`rounded-full object-cover ${sizeClass}`}
+              src={avatarURL}
+              alt={alt}
+            />
+          </TooltipWrapper>
+          <Tooltip>
+            <TooltipTrigger asChild>
+              <div
+                className={`absolute -bottom-[2px] -right-[2px] border-background rounded-full ${onlineStatusClass}`}
+              ></div>
+            </TooltipTrigger>
+            <TooltipContent sideOffset={-2}>
+              {online ? "online" : "offline"}
+            </TooltipContent>
+          </Tooltip>
+        </TooltipProvider>
+      </div>
+    </LinkWrapper>
+  );
 }
diff --git a/frontend/app/ui/user/match-history.tsx b/frontend/app/ui/user/match-history.tsx
index 77972a4c..1eee8f11 100644
--- a/frontend/app/ui/user/match-history.tsx
+++ b/frontend/app/ui/user/match-history.tsx
@@ -1,6 +1,5 @@
 import { getMatchHistory } from "@/app/lib/actions";
 import type { MatchDetailEntity } from "@/app/lib/dtos";
-import Link from "next/link";
 import { Avatar } from "./avatar";
 import ProfileItem from "./profile-item";
 
@@ -17,17 +16,19 @@ function MatchDetailItem({
       : "text-red-500"
     : "";
   return (
-    <Link href={`/user/${detail.user.id}`}>
-      <div className="flex flex-col gap-2">
-        <div className="flex gap-2 items-center">
-          <Avatar avatarURL={detail.user.avatarURL} size="medium" />
-          <div>{detail.user.name}</div>
-          <div className={`font-bold ${textColor}`}>
-            {detail.winLose} ({detail.score})
-          </div>
+    <div className="flex flex-col gap-2">
+      <div className="flex gap-2 items-center">
+        <Avatar
+          avatarURL={detail.user.avatarURL}
+          href={`/user/${detail.user.id}`}
+          size="medium"
+        />
+        <div>{detail.user.name}</div>
+        <div className={`font-bold ${textColor}`}>
+          {detail.winLose} ({detail.score})
         </div>
       </div>
-    </Link>
+    </div>
   );
 }
 
@@ -37,6 +38,7 @@ export default async function MatchHistory({ userId }: { userId: number }) {
     <ProfileItem title="Match History">
       <div className="flex flex-col gap-2">
         {history.map((match) => {
+          // TODO: player2 が undefinedでerrorになる
           return (
             <div key={match.id} className="flex gap-8 items-center">
               <MatchDetailItem
diff --git a/frontend/app/ui/user/user-list.tsx b/frontend/app/ui/user/user-list.tsx
index bd9c3d33..b623d621 100644
--- a/frontend/app/ui/user/user-list.tsx
+++ b/frontend/app/ui/user/user-list.tsx
@@ -1,7 +1,10 @@
+"use client";
+
 import type { PublicUserEntity } from "@/app/lib/dtos";
 import { TooltipProvider } from "@/components/ui/tooltip";
-import { AvatarSize } from "./avatar";
-import UserTooltip from "./user-tool-tip";
+import { Avatar, AvatarSize } from "./avatar";
+import { useEffect, useState } from "react";
+import { isOnline } from "@/app/lib/actions";
 
 export default function UserList({
   users,
@@ -10,12 +13,39 @@ export default function UserList({
   users: PublicUserEntity[];
   avatarSize: AvatarSize;
 }) {
+  const [onlineStatus, setOnlineStatus] = useState<{ [key: string]: boolean }>(
+    {},
+  );
+
+  const fetchOnlineStatus = async () => {
+    try {
+      users.forEach(async (u) => {
+        const body = await isOnline(u.id);
+        const online = body.isOnline;
+        setOnlineStatus((prev) => ({ ...prev, [u.name]: online }));
+      });
+    } catch (error) {
+      console.error("Error fetching online status:", error);
+    }
+  };
+
+  useEffect(() => {
+    fetchOnlineStatus();
+  }, []);
+
   return (
     <TooltipProvider delayDuration={0}>
       <div className="flex flex-wrap gap-2">
         {users.length === 0 && <div>No users to display</div>}
         {users.map((u) => (
-          <UserTooltip key={u.id} user={u} avatarSize={avatarSize} />
+          <Avatar
+            avatarURL={u.avatarURL}
+            size={avatarSize}
+            href={`/user/${u.id}`}
+            alt={u.name}
+            online={onlineStatus[u.name]}
+            key={u.id}
+          />
         ))}
       </div>
     </TooltipProvider>
diff --git a/frontend/app/ui/user/user-tool-tip.tsx b/frontend/app/ui/user/user-tool-tip.tsx
deleted file mode 100644
index 76f76ecd..00000000
--- a/frontend/app/ui/user/user-tool-tip.tsx
+++ /dev/null
@@ -1,32 +0,0 @@
-import type { PublicUserEntity } from "@/app/lib/dtos";
-import {
-  Tooltip,
-  TooltipContent,
-  TooltipTrigger,
-} from "@/components/ui/tooltip";
-import Link from "next/link";
-import { Avatar, AvatarSize } from "./avatar";
-
-// This component has to be used with TooltipProvider
-export default function UserTooltip({
-  user,
-  avatarSize,
-}: {
-  user: PublicUserEntity;
-  avatarSize: AvatarSize;
-}) {
-  return (
-    <Tooltip key={user.id}>
-      <TooltipTrigger>
-        <Link href={`/user/${user.id}`} key={user.id}>
-          <Avatar
-            avatarURL={user.avatarURL}
-            size={avatarSize}
-            alt={user.name}
-          />
-        </Link>
-      </TooltipTrigger>
-      <TooltipContent>{user.name}</TooltipContent>
-    </Tooltip>
-  );
-}