diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index a30ffbe0b2b91..f87e212eecbab 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -374,6 +374,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.wchar.wmemcmp
     libc.src.wchar.wmempcpy
     libc.src.wchar.wmemcpy
+    libc.src.wchar.wcscat
     libc.src.wchar.wcsstr
     libc.src.wchar.wcsncat
     libc.src.wchar.wcscpy
diff --git a/libc/include/wchar.yaml b/libc/include/wchar.yaml
index 29a989fddb592..a44a352e4753a 100644
--- a/libc/include/wchar.yaml
+++ b/libc/include/wchar.yaml
@@ -102,6 +102,13 @@ functions:
       - type: __restrict wchar_t *
       - type: const __restrict wchar_t *
       - type: size_t
+  - name: wcscat
+    standards:
+      - stdc
+    return_type: wchar_t *
+    arguments: 
+      - type: __restrict wchar_t *
+      - type: const __restrict wchar_t *
   - name: wcsstr
     standards:
       - stdc
diff --git a/libc/src/wchar/CMakeLists.txt b/libc/src/wchar/CMakeLists.txt
index be62495bf8a0f..95246ad777697 100644
--- a/libc/src/wchar/CMakeLists.txt
+++ b/libc/src/wchar/CMakeLists.txt
@@ -137,6 +137,18 @@ add_entrypoint_object(
     libc.src.__support.wctype_utils
 )
 
+add_entrypoint_object(
+  wcscat
+  SRCS
+    wcscat.cpp
+  HDRS
+    wcscat.h
+  DEPENDS
+    libc.hdr.types.size_t
+    libc.hdr.wchar_macros
+    libc.src.string.string_utils
+)
+
 add_entrypoint_object(
   wcsstr
   SRCS
diff --git a/libc/src/wchar/wcscat.cpp b/libc/src/wchar/wcscat.cpp
new file mode 100644
index 0000000000000..50d90c0941c75
--- /dev/null
+++ b/libc/src/wchar/wcscat.cpp
@@ -0,0 +1,29 @@
+//===-- Implementation of wcscat ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/wchar/wcscat.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/string/string_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(wchar_t *, wcscat,
+                   (wchar_t *__restrict s1, const wchar_t *__restrict s2)) {
+  size_t size_1 = internal::string_length(s1);
+  size_t i = 0;
+  for (; s2[i] != L'\0'; i++)
+    s1[size_1 + i] = s2[i];
+  s1[size_1 + i] = L'\0';
+  return s1;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/wchar/wcscat.h b/libc/src/wchar/wcscat.h
new file mode 100644
index 0000000000000..b0b4455983b4e
--- /dev/null
+++ b/libc/src/wchar/wcscat.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for wcscat ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WCSCAT_H
+#define LLVM_LIBC_SRC_WCHAR_WCSCAT_H
+
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+wchar_t *wcscat(wchar_t *__restrict s1, const wchar_t *__restrict s2);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSCAT_H
diff --git a/libc/test/src/wchar/CMakeLists.txt b/libc/test/src/wchar/CMakeLists.txt
index 38ff8b8720504..859d33a22617f 100644
--- a/libc/test/src/wchar/CMakeLists.txt
+++ b/libc/test/src/wchar/CMakeLists.txt
@@ -135,6 +135,16 @@ add_libc_test(
     libc.src.wchar.wmemcpy
 )
 
+add_libc_test(
+  wcscat_test
+  SUITE
+    libc_wchar_unittests
+  SRCS
+    wcscat_test.cpp
+  DEPENDS
+    libc.src.wchar.wcscat
+)
+  
 add_libc_test(
   wcsstr_test
   SUITE
diff --git a/libc/test/src/wchar/wcscat_test.cpp b/libc/test/src/wchar/wcscat_test.cpp
new file mode 100644
index 0000000000000..e91f79613ca9c
--- /dev/null
+++ b/libc/test/src/wchar/wcscat_test.cpp
@@ -0,0 +1,47 @@
+//===-- Unittests for wcscat ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "hdr/types/wchar_t.h"
+#include "src/wchar/wcscat.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcWCSCatTest, EmptyDest) {
+  // Dest should be fully replaced with src.
+  wchar_t dest[4] = {L'\0'};
+  const wchar_t *src = L"abc";
+  LIBC_NAMESPACE::wcscat(dest, src);
+  ASSERT_TRUE(dest[0] == L'a');
+  ASSERT_TRUE(dest[1] == L'b');
+  ASSERT_TRUE(dest[2] == L'c');
+  ASSERT_TRUE(dest[3] == L'\0');
+}
+
+TEST(LlvmLibcWCSCatTest, NonEmptyDest) {
+  // Src should be appended on to dest.
+  wchar_t dest[7] = {L'x', L'y', L'z', L'\0'};
+  const wchar_t *src = L"abc";
+  LIBC_NAMESPACE::wcscat(dest, src);
+  ASSERT_TRUE(dest[0] == L'x');
+  ASSERT_TRUE(dest[1] == L'y');
+  ASSERT_TRUE(dest[2] == L'z');
+  ASSERT_TRUE(dest[3] == L'a');
+  ASSERT_TRUE(dest[4] == L'b');
+  ASSERT_TRUE(dest[5] == L'c');
+  ASSERT_TRUE(dest[6] == L'\0');
+}
+
+TEST(LlvmLibcWCSCatTest, EmptySrc) {
+  // Dest should remain intact.
+  wchar_t dest[4] = {L'x', L'y', L'z', L'\0'};
+  const wchar_t *src = L"";
+  LIBC_NAMESPACE::wcscat(dest, src);
+  ASSERT_TRUE(dest[0] == L'x');
+  ASSERT_TRUE(dest[1] == L'y');
+  ASSERT_TRUE(dest[2] == L'z');
+  ASSERT_TRUE(dest[3] == L'\0');
+}