diff --git a/lib/winapi/Makefile b/lib/winapi/Makefile
index 78e993d73..47e8d2f1d 100644
--- a/lib/winapi/Makefile
+++ b/lib/winapi/Makefile
@@ -10,6 +10,7 @@ WINAPI_SRCS := \
 	$(NXDK_DIR)/lib/winapi/filemanip.c \
 	$(NXDK_DIR)/lib/winapi/findfile.c \
 	$(NXDK_DIR)/lib/winapi/handleapi.c \
+	$(NXDK_DIR)/lib/winapi/ioapi.c \
 	$(NXDK_DIR)/lib/winapi/memory.c \
 	$(NXDK_DIR)/lib/winapi/libloaderapi.c \
 	$(NXDK_DIR)/lib/winapi/profiling.c \
diff --git a/lib/winapi/fileio.c b/lib/winapi/fileio.c
index 5e600ad46..5eb4bf0a9 100644
--- a/lib/winapi/fileio.c
+++ b/lib/winapi/fileio.c
@@ -103,12 +103,42 @@ BOOL ReadFile (HANDLE hFile, LPVOID lpBuffer, DWORD nNumberOfBytesToRead, LPDWOR
     NTSTATUS status;
     IO_STATUS_BLOCK ioStatusBlock;
 
-    // overlapped I/O not supported yet
-    assert(!lpOverlapped);
+    if (lpOverlapped == NULL) {
+        // A null pointer makes the code crash on Windows, we'd rather catch it
+        assert(lpNumberOfBytesRead);
+    }
+
+    if (lpNumberOfBytesRead) {
+        *lpNumberOfBytesRead = 0;
+    }
+
+    if (lpOverlapped) {
+        LARGE_INTEGER overlappedOffset = {
+            .LowPart = lpOverlapped->Offset,
+            .HighPart = lpOverlapped->OffsetHigh,
+        };
+
+        // Internal contains the status code for the I/O request. Set to STATUS_PENDING at the start of the request.
+        lpOverlapped->Internal = (DWORD)STATUS_PENDING;
+        // InternalHigh contains the actual number of bytes transferred for the I/O request
+        lpOverlapped->InternalHigh = 0;
 
-    // A null pointer makes the code crash on Windows, we'd rather catch it
-    assert(lpNumberOfBytesRead);
-    *lpNumberOfBytesRead = 0;
+        status = NtReadFile(hFile, lpOverlapped->hEvent, NULL, NULL, (PIO_STATUS_BLOCK)&lpOverlapped->Internal,
+                            lpBuffer, nNumberOfBytesToRead, &overlappedOffset);
+
+        // The read can finish immediately. Handle this case
+        if (NT_SUCCESS(status) && status != STATUS_PENDING) {
+            if (lpNumberOfBytesRead) {
+                *lpNumberOfBytesRead = (DWORD)lpOverlapped->InternalHigh;
+            }
+            return TRUE;
+        } else if (status == STATUS_END_OF_FILE) {
+            *lpNumberOfBytesRead = 0;
+            return TRUE;
+        }
+        SetLastError(RtlNtStatusToDosError(status));
+        return FALSE;
+    }
 
     status = NtReadFile(hFile, NULL, NULL, NULL, &ioStatusBlock, lpBuffer, nNumberOfBytesToRead, NULL);
 
@@ -139,12 +169,39 @@ BOOL WriteFile (HANDLE hFile, LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite, LPD
     NTSTATUS status;
     IO_STATUS_BLOCK ioStatusBlock;
 
-    // overlapped I/O not supported yet
-    assert(!lpOverlapped);
+    if (lpOverlapped == NULL) {
+        // A null pointer makes the code crash on Windows, we'd rather catch it
+        assert(lpNumberOfBytesWritten);
+    }
+
+    if (lpNumberOfBytesWritten) {
+        *lpNumberOfBytesWritten = 0;
+    }
+
+    if (lpOverlapped) {
+        LARGE_INTEGER overlappedOffset = {
+            .LowPart = lpOverlapped->Offset,
+            .HighPart = lpOverlapped->OffsetHigh,
+        };
+
+        // Internal contains the status code for the I/O request. Set to STATUS_PENDING at the start of the request
+        lpOverlapped->Internal = (DWORD)STATUS_PENDING;
+        // InternalHigh contains the actual number of bytes transferred for the I/O request
+        lpOverlapped->InternalHigh = 0;
+
+        status = NtWriteFile(hFile, lpOverlapped->hEvent, NULL, NULL, (PIO_STATUS_BLOCK)&lpOverlapped->Internal,
+                            (PVOID)lpBuffer, nNumberOfBytesToWrite, &overlappedOffset);
 
-    // A null pointer makes the code crash on Windows, we'd rather catch it
-    assert(lpNumberOfBytesWritten);
-    *lpNumberOfBytesWritten = 0;
+        // The write can finish immediately. Handle this case
+        if (NT_SUCCESS(status) && status != STATUS_PENDING) {
+            if (lpNumberOfBytesWritten) {
+                *lpNumberOfBytesWritten = (DWORD)lpOverlapped->InternalHigh;
+            }
+            return TRUE;
+        }
+        SetLastError(RtlNtStatusToDosError(status));
+        return FALSE;
+    }
 
     status = NtWriteFile(hFile, NULL, NULL, NULL, &ioStatusBlock, (PVOID)lpBuffer, nNumberOfBytesToWrite, NULL);
 
diff --git a/lib/winapi/ioapi.c b/lib/winapi/ioapi.c
new file mode 100644
index 000000000..eae069803
--- /dev/null
+++ b/lib/winapi/ioapi.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: MIT
+
+// SPDX-FileCopyrightText: 2023 Ryan Wendland
+
+#include <synchapi.h>
+#include <winbase.h>
+#include <winerror.h>
+#include <xboxkrnl/xboxkrnl.h>
+
+BOOL GetOverlappedResult (HANDLE hFile, LPOVERLAPPED lpOverlapped, LPDWORD lpNumberOfBytesTransferred, BOOL bWait)
+{
+    DWORD status;
+    HANDLE waitHandle;
+
+    status = (DWORD)lpOverlapped->Internal;
+
+    if (status == STATUS_PENDING && bWait == FALSE) {
+        SetLastError(ERROR_IO_INCOMPLETE);
+        return FALSE;
+    }
+
+    // If the hEvent member of the OVERLAPPED structure is NULL, the system
+    // uses the state of the hFile handle to signal when the operation has been completed
+    if (lpOverlapped->hEvent == NULL) {
+        waitHandle = hFile;
+    } else {
+        waitHandle = lpOverlapped->hEvent;
+    }
+
+    if (status == STATUS_PENDING) {
+        if (WaitForSingleObject(waitHandle, INFINITE) != WAIT_OBJECT_0) {
+            SetLastError(ERROR_IO_INCOMPLETE);
+            return FALSE;
+        }
+        // Get final status of the transfer
+        status = (DWORD)lpOverlapped->Internal;
+    }
+
+    // InternalHigh contains the actual number of bytes transferred for the I/O request
+    *lpNumberOfBytesTransferred = (DWORD)lpOverlapped->InternalHigh;
+
+    if (!NT_SUCCESS(status)) {
+        SetLastError(RtlNtStatusToDosError(status));
+        return FALSE;
+    }
+    return TRUE;
+}
diff --git a/lib/winapi/winbase.h b/lib/winapi/winbase.h
index 063596fbe..e7afcd09a 100644
--- a/lib/winapi/winbase.h
+++ b/lib/winapi/winbase.h
@@ -134,6 +134,8 @@ void WINAPI OutputDebugStringA (LPCTSTR lpOutputString);
 
 BOOL IsBadWritePtr (LPVOID lp, UINT_PTR ucb);
 
+BOOL GetOverlappedResult (HANDLE hFile, LPOVERLAPPED lpOverlapped, LPDWORD lpNumberOfBytesTransferred, BOOL bWait);
+
 #ifndef UNICODE
 #define OutputDebugString OutputDebugStringA
 #else