diff --git a/envoy/api/os_sys_calls.h b/envoy/api/os_sys_calls.h
index 28a591307443b..6a26a19edc70a 100644
--- a/envoy/api/os_sys_calls.h
+++ b/envoy/api/os_sys_calls.h
@@ -149,6 +149,11 @@ class OsSysCalls {
    */
   virtual SysCallIntResult stat(const char* pathname, struct stat* buf) PURE;
 
+  /**
+   * @see man 2 fstat
+   */
+  virtual SysCallIntResult fstat(os_fd_t fd, struct stat* buf) PURE;
+
   /**
    * @see man 2 setsockopt
    */
diff --git a/source/common/api/posix/os_sys_calls_impl.cc b/source/common/api/posix/os_sys_calls_impl.cc
index 3afac06a4c685..a142f949a61e7 100644
--- a/source/common/api/posix/os_sys_calls_impl.cc
+++ b/source/common/api/posix/os_sys_calls_impl.cc
@@ -194,6 +194,11 @@ SysCallIntResult OsSysCallsImpl::stat(const char* pathname, struct stat* buf) {
   return {rc, rc != -1 ? 0 : errno};
 }
 
+SysCallIntResult OsSysCallsImpl::fstat(os_fd_t fd, struct stat* buf) {
+  const int rc = ::fstat(fd, buf);
+  return {rc, rc != -1 ? 0 : errno};
+}
+
 SysCallIntResult OsSysCallsImpl::setsockopt(os_fd_t sockfd, int level, int optname,
                                             const void* optval, socklen_t optlen) {
   const int rc = ::setsockopt(sockfd, level, optname, optval, optlen);
diff --git a/source/common/api/posix/os_sys_calls_impl.h b/source/common/api/posix/os_sys_calls_impl.h
index 61a79c8aab063..0c4491eab7996 100644
--- a/source/common/api/posix/os_sys_calls_impl.h
+++ b/source/common/api/posix/os_sys_calls_impl.h
@@ -35,6 +35,7 @@ class OsSysCallsImpl : public OsSysCalls {
   SysCallPtrResult mmap(void* addr, size_t length, int prot, int flags, int fd,
                         off_t offset) override;
   SysCallIntResult stat(const char* pathname, struct stat* buf) override;
+  SysCallIntResult fstat(os_fd_t fd, struct stat* buf) override;
   SysCallIntResult setsockopt(os_fd_t sockfd, int level, int optname, const void* optval,
                               socklen_t optlen) override;
   SysCallIntResult getsockopt(os_fd_t sockfd, int level, int optname, void* optval,
diff --git a/source/common/api/win32/os_sys_calls_impl.cc b/source/common/api/win32/os_sys_calls_impl.cc
index 1a630b5d9c6b6..69502f12cff28 100644
--- a/source/common/api/win32/os_sys_calls_impl.cc
+++ b/source/common/api/win32/os_sys_calls_impl.cc
@@ -114,8 +114,14 @@ SysCallIntResult OsSysCallsImpl::ioctl(os_fd_t sockfd, unsigned long control_cod
 }
 
 SysCallIntResult OsSysCallsImpl::close(os_fd_t fd) {
-  const int rc = ::closesocket(fd);
-  return {rc, rc != -1 ? 0 : ::WSAGetLastError()};
+  int rc = ::closesocket(fd);
+  const int socket_err = ::WSAGetLastError();
+  if (rc == -1) {
+    // If `closesocket` failed, maybe the descriptor was a file.
+    rc = ::close(fd);
+  }
+  // Assume the descriptor was a socket, and return the error from that one, if both failed.
+  return {rc, rc != -1 ? 0 : socket_err};
 }
 
 SysCallSizeResult OsSysCallsImpl::writev(os_fd_t fd, const iovec* iov, int num_iov) {
@@ -226,6 +232,11 @@ SysCallIntResult OsSysCallsImpl::stat(const char* pathname, struct stat* buf) {
   return {rc, rc != -1 ? 0 : errno};
 }
 
+SysCallIntResult OsSysCallsImpl::fstat(os_fd_t fd, struct stat* buf) {
+  const int rc = ::fstat(fd, buf);
+  return {rc, rc != -1 ? 0 : errno};
+}
+
 SysCallIntResult OsSysCallsImpl::setsockopt(os_fd_t sockfd, int level, int optname,
                                             const void* optval, socklen_t optlen) {
   const int rc = ::setsockopt(sockfd, level, optname, static_cast<const char*>(optval), optlen);
diff --git a/source/common/api/win32/os_sys_calls_impl.h b/source/common/api/win32/os_sys_calls_impl.h
index 44bc4993709f8..2afa41dd2ce3b 100644
--- a/source/common/api/win32/os_sys_calls_impl.h
+++ b/source/common/api/win32/os_sys_calls_impl.h
@@ -36,6 +36,7 @@ class OsSysCallsImpl : public OsSysCalls {
   SysCallPtrResult mmap(void* addr, size_t length, int prot, int flags, int fd,
                         off_t offset) override;
   SysCallIntResult stat(const char* pathname, struct stat* buf) override;
+  SysCallIntResult fstat(os_fd_t fd, struct stat* buf) override;
   SysCallIntResult setsockopt(os_fd_t sockfd, int level, int optname, const void* optval,
                               socklen_t optlen) override;
   SysCallIntResult getsockopt(os_fd_t sockfd, int level, int optname, void* optval,
diff --git a/test/common/api/os_sys_calls_test.cc b/test/common/api/os_sys_calls_test.cc
index 5748b257ac791..432a43b737e02 100644
--- a/test/common/api/os_sys_calls_test.cc
+++ b/test/common/api/os_sys_calls_test.cc
@@ -1,9 +1,73 @@
+#ifdef WIN32
+#include <fcntl.h> // Needed for `O_CREAT` and `O_RDWR` on Win32.
+
+#endif
+
 #include "source/common/api/os_sys_calls_impl.h"
 
+#include "test/test_common/environment.h"
+
 #include "gtest/gtest.h"
 
 namespace Envoy {
 
+// Test happy path for `open`, `pwrite`, `pread`, `fstat`, `close`, `stat` and `unlink`.
+TEST(OsSyscallsTest, OpenPwritePreadFstatCloseStatUnlink) {
+  auto& os_syscalls = Api::OsSysCallsSingleton::get();
+  std::string path{TestEnvironment::temporaryPath("envoy_test")};
+  TestEnvironment::createPath(path);
+  std::string file_path = path + "/file";
+  absl::string_view file_contents = "12345";
+// Test `open`
+#ifdef WIN32
+  int pmode = _S_IWRITE | _S_IREAD;
+#else
+  int pmode = S_IRUSR | S_IWUSR;
+#endif
+  Api::SysCallIntResult open_result = os_syscalls.open(file_path.c_str(), O_CREAT | O_RDWR, pmode);
+  EXPECT_NE(open_result.return_value_, -1);
+  EXPECT_EQ(open_result.errno_, 0);
+  os_fd_t fd = open_result.return_value_;
+#ifdef WIN32
+  // `pwrite` and `pread` are not supported. Just write some bytes so we can still test stat.
+  EXPECT_EQ(file_contents.size(), ::_write(fd, file_contents.begin(), file_contents.size()));
+#else
+  // Test `pwrite`
+  Api::SysCallSizeResult write_result =
+      os_syscalls.pwrite(fd, file_contents.begin(), file_contents.size(), 0);
+  EXPECT_EQ(write_result.return_value_, file_contents.size());
+  EXPECT_EQ(write_result.errno_, 0);
+  // Test `pread`
+  char read_buffer[5];
+  Api::SysCallSizeResult read_result = os_syscalls.pread(fd, read_buffer, sizeof(read_buffer), 0);
+  EXPECT_EQ(read_result.return_value_, sizeof(read_buffer));
+  EXPECT_EQ(read_result.errno_, 0);
+  absl::string_view read_buffer_view{read_buffer, sizeof(read_buffer)};
+  EXPECT_EQ(file_contents, read_buffer_view);
+#endif
+  // Test `fstat`
+  struct stat fstat_value;
+  Api::SysCallIntResult fstat_result = os_syscalls.fstat(fd, &fstat_value);
+  EXPECT_EQ(fstat_result.return_value_, 0);
+  EXPECT_EQ(fstat_result.errno_, 0);
+  EXPECT_EQ(fstat_value.st_size, file_contents.size());
+  // Test `close`
+  Api::SysCallIntResult close_result = os_syscalls.close(fd);
+  EXPECT_EQ(close_result.return_value_, 0);
+  EXPECT_EQ(close_result.errno_, 0);
+  // Test `stat`
+  struct stat stat_value;
+  Api::SysCallIntResult stat_result = os_syscalls.stat(file_path.c_str(), &stat_value);
+  EXPECT_EQ(stat_result.return_value_, 0);
+  EXPECT_EQ(stat_result.errno_, 0);
+  EXPECT_EQ(stat_value.st_size, file_contents.size());
+  // Test `unlink`
+  Api::SysCallIntResult unlink_result = os_syscalls.unlink(file_path.c_str());
+  EXPECT_EQ(unlink_result.return_value_, 0);
+  EXPECT_EQ(unlink_result.errno_, 0);
+  TestEnvironment::removePath(path);
+}
+
 TEST(OsSyscallsTest, SetAlternateGetifaddrs) {
   auto& os_syscalls = Api::OsSysCallsSingleton::get();
   const bool pre_alternate_support = os_syscalls.supportsGetifaddrs();
diff --git a/test/mocks/api/mocks.h b/test/mocks/api/mocks.h
index 7d136a0784237..95f8bf8a8a179 100644
--- a/test/mocks/api/mocks.h
+++ b/test/mocks/api/mocks.h
@@ -94,6 +94,7 @@ class MockOsSysCalls : public OsSysCallsImpl {
   MOCK_METHOD(SysCallPtrResult, mmap,
               (void* addr, size_t length, int prot, int flags, int fd, off_t offset));
   MOCK_METHOD(SysCallIntResult, stat, (const char* name, struct stat* stat));
+  MOCK_METHOD(SysCallIntResult, fstat, (os_fd_t fd, struct stat* stat));
   MOCK_METHOD(SysCallIntResult, chmod, (const std::string& name, mode_t mode));
   MOCK_METHOD(int, setsockopt_,
               (os_fd_t sockfd, int level, int optname, const void* optval, socklen_t optlen));