diff --git a/command.ts b/command.ts
index ab41537a..054e7483 100644
--- a/command.ts
+++ b/command.ts
@@ -178,9 +178,20 @@ export type SScanOpts = BaseScanOpts;
 export type ZScanOpts = BaseScanOpts;
 
 export interface ZAddOpts {
+  /** @deprecated Use {@linkcode ZAddOpts.nx}/{@linkcode ZAddOpts.xx} instead. This option will be removed in the future. */
   mode?: "NX" | "XX";
   ch?: boolean;
+  /** Enables `NX` option */
+  nx?: boolean;
+  /** Enables `XX` option */
+  xx?: boolean;
 }
+/** Return type for {@linkcode RedisCommands.zadd} */
+export type ZAddReply<T extends ZAddOpts> = T extends { mode: "NX" | "XX" }
+  ? Integer | BulkNil
+  : T extends { nx: true } ? Integer | BulkNil
+  : T extends { xx: true } ? Integer | BulkNil
+  : Integer;
 
 interface ZStoreOpts {
   aggregate?: "SUM" | "MIN" | "MAX";
@@ -1006,22 +1017,22 @@ XRANGE somestream - +
     timeout: number,
     ...keys: string[]
   ): Promise<[BulkString, BulkString, BulkString] | BulkNil>;
-  zadd(
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     score: number,
     member: RedisValue,
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
-  zadd(
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     score_members: [number, RedisValue][],
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
-  zadd(
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     member_scores: Record<string | number, number>,
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
   zaddIncr(
     key: string,
     score: number,
diff --git a/mod.ts b/mod.ts
index a6055956..df274c03 100644
--- a/mod.ts
+++ b/mod.ts
@@ -46,6 +46,7 @@ export type {
   StralgoOpts,
   StralgoTarget,
   ZAddOpts,
+  ZAddReply,
   ZInterOpts,
   ZInterstoreOpts,
   ZRangeByLexOpts,
diff --git a/protocol/deno_streams/reply.ts b/protocol/deno_streams/reply.ts
index 1ffbad84..b0eae69b 100644
--- a/protocol/deno_streams/reply.ts
+++ b/protocol/deno_streams/reply.ts
@@ -65,6 +65,7 @@ async function readBulkReply(
   }
 
   const size = parseSize(line);
+  console.info("bulkReply", { size, line: new TextDecoder().decode(line) });
   if (size < 0) {
     // nil bulk reply
     return null;
diff --git a/redis.ts b/redis.ts
index 821ac4be..36789651 100644
--- a/redis.ts
+++ b/redis.ts
@@ -33,6 +33,7 @@ import type {
   StralgoOpts,
   StralgoTarget,
   ZAddOpts,
+  ZAddReply,
   ZInterOpts,
   ZInterstoreOpts,
   ZRangeByLexOpts,
@@ -2095,22 +2096,22 @@ class RedisImpl implements Redis {
     return this.execIntegerReply("XTRIM", key, "MAXLEN", ...args);
   }
 
-  zadd(
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     score: number,
     member: string,
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
-  zadd(
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     scoreMembers: [number, string][],
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
-  zadd(
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
+  zadd<TZAddOpts extends ZAddOpts = ZAddOpts>(
     key: string,
     memberScores: Record<string, number>,
-    opts?: ZAddOpts,
-  ): Promise<Integer>;
+    opts?: TZAddOpts,
+  ): Promise<ZAddReply<TZAddOpts>>;
   zadd(
     key: string,
     param1: number | [number, string][] | Record<string, number>,
@@ -2118,32 +2119,44 @@ class RedisImpl implements Redis {
     opts?: ZAddOpts,
   ) {
     const args: (string | number)[] = [key];
+    let isAbleToReturnNil = false;
     if (Array.isArray(param1)) {
-      this.pushZAddOpts(args, param2 as ZAddOpts);
+      isAbleToReturnNil = this.pushZAddOpts(args, param2 as ZAddOpts);
       args.push(...param1.flatMap((e) => e));
       opts = param2 as ZAddOpts;
     } else if (typeof param1 === "object") {
-      this.pushZAddOpts(args, param2 as ZAddOpts);
+      isAbleToReturnNil = this.pushZAddOpts(args, param2 as ZAddOpts);
       for (const [member, score] of Object.entries(param1)) {
         args.push(score as number, member);
       }
     } else {
-      this.pushZAddOpts(args, opts);
+      isAbleToReturnNil = this.pushZAddOpts(args, opts);
       args.push(param1, param2 as string);
     }
-    return this.execIntegerReply("ZADD", ...args);
+    return isAbleToReturnNil
+      ? this.execIntegerOrNilReply("ZADD", ...args)
+      : this.execIntegerReply("ZADD", ...args);
   }
 
   private pushZAddOpts(
     args: (string | number)[],
     opts?: ZAddOpts,
-  ): void {
-    if (opts?.mode) {
+  ): boolean {
+    let isAbleToReturnNil = false;
+    if (opts?.nx) {
+      args.push("NX");
+      isAbleToReturnNil = true;
+    } else if (opts?.xx) {
+      args.push("XX");
+      isAbleToReturnNil = true;
+    } else if (opts?.mode) {
       args.push(opts.mode);
+      isAbleToReturnNil = true;
     }
     if (opts?.ch) {
       args.push("CH");
     }
+    return isAbleToReturnNil;
   }
 
   zaddIncr(
diff --git a/tests/commands/sorted_set.ts b/tests/commands/sorted_set.ts
index 72a9b2b5..a98fe685 100644
--- a/tests/commands/sorted_set.ts
+++ b/tests/commands/sorted_set.ts
@@ -1,5 +1,13 @@
 import { assert, assertEquals } from "../../deps/std/assert.ts";
-import { afterAll, beforeAll, beforeEach, it } from "../../deps/std/testing.ts";
+import type { IsExact } from "../../deps/std/testing.ts";
+import {
+  afterAll,
+  assertType,
+  beforeAll,
+  beforeEach,
+  describe,
+  it,
+} from "../../deps/std/testing.ts";
 import type { Connector, TestServer } from "../test_util.ts";
 import type { Redis } from "../../mod.ts";
 
@@ -39,35 +47,59 @@ export function zsetTests(
     assertEquals(arr, null);
   });
 
-  it("zadd", async () => {
-    assertEquals(await client.zadd("key", { "1": 1, "2": 2 }), 2);
-    assertEquals(await client.zadd("key", 3, "3"), 1);
-    assertEquals(
-      await client.zadd("key", [
+  describe("zadd", () => {
+    it("adds specified members to a sorted set", async () => {
+      const v = await client.zadd("key", { "1": 1, "2": 2 });
+      assertEquals(v, 2);
+
+      const v2 = await client.zadd("key", 3, "3");
+      assertEquals(v2, 1);
+
+      const v3 = await client.zadd("key", [
         [4, "4"],
         [5, "5"],
-      ]),
-      2,
-    );
-  });
+      ]);
+      assertEquals(
+        v3,
+        2,
+      );
+      assertType<IsExact<typeof v3, number>>(true);
+    });
 
-  it("zaddWithMode", async () => {
-    assertEquals(await client.zadd("key", 1, "1", { mode: "NX" }), 1);
-    assertEquals(await client.zadd("key", { "1": 1 }, { mode: "XX" }), 0);
-    assertEquals(
-      await client.zadd("key", [[1, "1"], [2, "2"]], { mode: "NX" }),
-      1,
-    );
-  });
+    it("supports `NX` and `XX`", async () => {
+      const v = await client.zadd("zaddWithNXOrXX", 1, "1", { nx: true });
+      assertEquals(v, 1);
+      assertType<IsExact<typeof v, number | null>>(true);
 
-  it("zaddWithCH", async () => {
-    assertEquals(await client.zadd("key", [[1, "foo"], [2, "bar"]]), 2);
-    assertEquals(
-      await client.zadd("key", { "foo": 1, "bar": 3, "baz": 4 }, { ch: true }),
-      2,
-    );
-  });
+      const v2 = await client.zadd("zaddWithNXOrXX", 2, "1", { mode: "NX" });
+      assertEquals(v2, null);
+      assertType<IsExact<typeof v2, number | null>>(true);
 
+      const v3 = await client.zadd("zaddWithNXOrXX", 3, "1", { xx: true });
+      assertEquals(v3, 1);
+      assertType<IsExact<typeof v3, number | null>>(true);
+
+      const v4 = await client.zadd("zaddWithNXOrXX", [[1, "2"]], {
+        mode: "NX",
+      });
+      assertEquals(v4, null);
+      assertType<IsExact<typeof v4, number | null>>(true);
+    });
+
+    it("supports `CH`", async () => {
+      assertEquals(await client.zadd("keyWithCH", [[1, "foo"], [2, "bar"]]), 2);
+      const v = await client.zadd(
+        "keyWithCH",
+        { "foo": 1, "bar": 3, "baz": 4 },
+        { ch: true },
+      );
+      assertEquals(
+        v,
+        2,
+      );
+      assertType<IsExact<typeof v, number>>(true);
+    });
+  });
   it("zaddIncr", async () => {
     await client.zadd("key", 1, "a");
     await client.zaddIncr("key", 2, "a");