diff --git a/modules/rostests/apitests/kernel32/CMakeLists.txt b/modules/rostests/apitests/kernel32/CMakeLists.txt
index bba783049c3..368c4d7eb90 100644
--- a/modules/rostests/apitests/kernel32/CMakeLists.txt
+++ b/modules/rostests/apitests/kernel32/CMakeLists.txt
@@ -17,6 +17,7 @@ list(APPEND SOURCE
     GetCPInfo.c
     GetCurrentDirectory.c
     GetDriveType.c
+    GetEnvironmentVariable.c
     GetFinalPathNameByHandle.c
     GetLocaleInfo.c
     GetModuleFileName.c
diff --git a/modules/rostests/apitests/kernel32/GetEnvironmentVariable.c b/modules/rostests/apitests/kernel32/GetEnvironmentVariable.c
new file mode 100644
index 00000000000..8dff7c991bf
--- /dev/null
+++ b/modules/rostests/apitests/kernel32/GetEnvironmentVariable.c
@@ -0,0 +1,125 @@
+/*
+ * PROJECT:     ReactOS API tests
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Tests for GetEnvironmentVariable(A/W)
+ * COPYRIGHT:   Copyright 2026 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#include "precomp.h"
+
+static void Test_GetEnvironmentVariableA(void)
+{
+    CHAR Buffer[MAX_PATH];
+    ULONG ActualLength, Length;
+
+    /* Get the COMSPEC variable */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableA("COMSPEC", Buffer, ARRAYSIZE(Buffer));
+    Buffer[MAX_PATH - 1] = '\0';
+    ActualLength = (ULONG)strlen(Buffer);
+    ok(ActualLength < ARRAYSIZE(Buffer) - 1, "ActualLength == ARRAYSIZE(Buffer) - 1. Not null-terminated?\n");
+    ok_eq_ulong(Length, ActualLength);
+    ok_eq_char(Buffer[ActualLength + 1], '\xAB');
+
+    /* Get the length only (return value is including NULL char) */
+    Length = GetEnvironmentVariableA("COMSPEC", NULL, 0);
+    ok_eq_ulong(Length, ActualLength + 1);
+
+    /* Test a buffer size that is too small */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableA("COMSPEC", Buffer, 5);
+    ok_eq_ulong(Length, ActualLength + 1);
+    ok_eq_char(Buffer[0], '\xAB');
+
+    /* Test a buffer size that doesn't fit the terminating NULL char */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableA("COMSPEC", Buffer, ActualLength);
+    ok_eq_ulong(Length, ActualLength + 1);
+    ok_eq_char(Buffer[0], '\xAB');
+
+    /* Test a buffer size that is just large enough */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableA("COMSPEC", Buffer, ActualLength + 1);
+    ok_eq_ulong(Length, ActualLength);
+    ok_eq_wchar(Buffer[ActualLength], '\0');
+    ok_eq_wchar(Buffer[ActualLength + 1], '\xAB');
+
+    /* Test non-existant variable name */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableA("ThisVariableDoesNotExit", Buffer, ARRAYSIZE(Buffer));
+    ok_eq_ulong(Length, 0);
+    ok_eq_wchar(Buffer[0], '\xAB');
+
+    /* Test NULL variable name */
+    Length = GetEnvironmentVariableA(NULL, Buffer, ARRAYSIZE(Buffer));
+    ok_eq_ulong(Length, 0);
+
+    /* Test NULL buffer with non-null size */
+    StartSeh()
+        Length = GetEnvironmentVariableA("COMSPEC", NULL, ARRAYSIZE(Buffer));
+    EndSeh(STATUS_ACCESS_VIOLATION);
+}
+
+static void Test_GetEnvironmentVariableW(void)
+{
+    WCHAR Buffer[MAX_PATH];
+    ULONG ActualLength, Length;
+
+    /* Get the COMSPEC variable */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableW(L"COMSPEC", Buffer, ARRAYSIZE(Buffer));
+    Buffer[MAX_PATH - 1] = L'\0';
+    ActualLength = (ULONG)wcslen(Buffer);
+    ok(ActualLength < ARRAYSIZE(Buffer) - 1, "ActualLength == ARRAYSIZE(Buffer) - 1. Not null-terminated?\n");
+    ok_eq_ulong(Length, ActualLength);
+    ok_eq_wchar(Buffer[ActualLength + 1], 0xABAB);
+
+    /* Get the length only (return value is including NULL char) */
+    Length = GetEnvironmentVariableW(L"COMSPEC", NULL, 0);
+    ok_eq_ulong(Length, ActualLength + 1);
+
+    /* Test a buffer size that is too small */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableW(L"COMSPEC", Buffer, 2);
+    ok_eq_ulong(Length, ActualLength + 1);
+    ok(Buffer[0] == UNICODE_NULL || broken(/* Windows 2003 */ Buffer[0] == 0xABAB), "Buffer[0] = 0x%x\n", Buffer[0]);
+    ok_eq_wchar(Buffer[1], 0xABAB);
+
+    /* Test a buffer size that doesn't fit the terminating NULL char */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableW(L"COMSPEC", Buffer, ActualLength);
+    ok_eq_ulong(Length, ActualLength + 1);
+    ok(Buffer[0] == UNICODE_NULL || broken(/* Windows 2003 */ Buffer[0] == 0xABAB), "Buffer[0] = 0x%x\n", Buffer[0]);
+    ok_eq_wchar(Buffer[1], 0xABAB);
+
+    /* Test a buffer size that is just large enough */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableW(L"COMSPEC", Buffer, ActualLength + 1);
+    ok_eq_ulong(Length, ActualLength);
+    ok_eq_wchar(Buffer[ActualLength], L'\0');
+    ok_eq_wchar(Buffer[ActualLength + 1], 0xABAB);
+
+    /* Test non-existant variable name */
+    memset(Buffer, 0xAB, sizeof(Buffer));
+    Length = GetEnvironmentVariableW(L"ThisVariableDoesNotExit", Buffer, ARRAYSIZE(Buffer));
+    ok_eq_ulong(Length, 0);
+    ok_eq_wchar(Buffer[0], 0xABAB);
+
+    /* Test NULL variable name */
+    StartSeh()
+        Length = GetEnvironmentVariableW(NULL, Buffer, ARRAYSIZE(Buffer));
+    EndSeh(STATUS_SUCCESS);
+    ok_eq_ulong(Length, 0);
+
+    /* Test NULL buffer with non-null size */
+    StartSeh()
+        Length = GetEnvironmentVariableW(L"COMSPEC", NULL, ARRAYSIZE(Buffer));
+    EndSeh(STATUS_SUCCESS);
+    ok((Length == ActualLength + 1) || broken(/* Windows 2003 */ Length == 0), "Length == %lu, ActualLength == %lu\n", Length, ActualLength);
+}
+
+START_TEST(GetEnvironmentVariable)
+{
+    Test_GetEnvironmentVariableA();
+    Test_GetEnvironmentVariableW();
+}
diff --git a/modules/rostests/apitests/kernel32/testlist.c b/modules/rostests/apitests/kernel32/testlist.c
index 3bec920a41c..2f9efc0634d 100644
--- a/modules/rostests/apitests/kernel32/testlist.c
+++ b/modules/rostests/apitests/kernel32/testlist.c
@@ -16,6 +16,7 @@ extern void func_GetComputerNameEx(void);
 extern void func_GetCPInfo(void);
 extern void func_GetCurrentDirectory(void);
 extern void func_GetDriveType(void);
+extern void func_GetEnvironmentVariable(void);
 extern void func_GetFinalPathNameByHandle(void);
 extern void func_GetLocaleInfo(void);
 extern void func_GetModuleFileName(void);
@@ -60,6 +61,7 @@ const struct test winetest_testlist[] =
     { "GetCPInfo",                   func_GetCPInfo },
     { "GetCurrentDirectory",         func_GetCurrentDirectory },
     { "GetDriveType",                func_GetDriveType },
+    { "GetEnvironmentVariable",      func_GetEnvironmentVariable },
     { "GetFinalPathNameByHandle",    func_GetFinalPathNameByHandle },
     { "GetLocaleInfo",               func_GetLocaleInfo },
     { "GetModuleFileName",           func_GetModuleFileName },