diff --git a/asio/include/asio/detail/impl/posix_thread.ipp b/asio/include/asio/detail/impl/posix_thread.ipp
index c38f531c97..c3c8d76eea 100644
--- a/asio/include/asio/detail/impl/posix_thread.ipp
+++ b/asio/include/asio/detail/impl/posix_thread.ipp
@@ -3,6 +3,7 @@
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+// Copyright (c) 2025 Pavlo Kleymonov (pkleymonov at qnx dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -47,6 +48,11 @@ std::size_t posix_thread::hardware_concurrency()
 {
 #if defined(_SC_NPROCESSORS_ONLN)
   long result = sysconf(_SC_NPROCESSORS_ONLN);
+
+#if defined(__QNX__)
+  result &= 0xFFFFFFFF;
+#endif //defined(__QNX__)
+
   if (result > 0)
     return result;
 #endif // defined(_SC_NPROCESSORS_ONLN)
diff --git a/asio/include/asio/detail/socket_types.hpp b/asio/include/asio/detail/socket_types.hpp
index c1be3777b9..060f2269a8 100644
--- a/asio/include/asio/detail/socket_types.hpp
+++ b/asio/include/asio/detail/socket_types.hpp
@@ -3,6 +3,7 @@
 // ~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+// Copyright (c) 2025 Pavlo Kleymonov (pkleymonov at qnx dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -411,7 +412,13 @@ const int max_iov_len = IOV_MAX;
 // POSIX platforms are not required to define IOV_MAX.
 const int max_iov_len = 16;
 # endif
-# define ASIO_OS_DEF_SA_RESTART SA_RESTART
+// Note: QNX does not support SA_RESTART
+// Therefore they are specifically excluded here.
+# if defined(__QNX__)
+#  define ASIO_OS_DEF_SA_RESTART 0
+# else
+#  define ASIO_OS_DEF_SA_RESTART SA_RESTART
+# endif
 # define ASIO_OS_DEF_SA_NOCLDSTOP SA_NOCLDSTOP
 # define ASIO_OS_DEF_SA_NOCLDWAIT SA_NOCLDWAIT
 #endif
diff --git a/asio/src/examples/cpp11/local/fd_passing_stream_client.cpp b/asio/src/examples/cpp11/local/fd_passing_stream_client.cpp
index 0473040b4e..9c68a9f3d1 100644
--- a/asio/src/examples/cpp11/local/fd_passing_stream_client.cpp
+++ b/asio/src/examples/cpp11/local/fd_passing_stream_client.cpp
@@ -4,6 +4,7 @@
 //
 // Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 // Copyright (c) 2021 Heiko Hund (heiko at openvpn dot net)
+// Copyright (c) 2025 Pavlo Kleymonov (pkleymonov at qnx dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -23,6 +24,14 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 
+#if defined(__QNX__)
+   #undef CMSG_ALIGN
+   #define CMSG_ALIGN(len) (((len) + sizeof (size_t) - 1) & (size_t) ~(sizeof (size_t) - 1))
+
+   #undef CMSG_SPACE
+   #define CMSG_SPACE(len) (CMSG_ALIGN (len) + CMSG_ALIGN (sizeof (struct cmsghdr)))
+#endif //defined(__QNX__)
+
 using asio::local::stream_protocol;
 
 constexpr std::size_t max_length = 1024;
diff --git a/asio/src/examples/cpp11/local/fd_passing_stream_server.cpp b/asio/src/examples/cpp11/local/fd_passing_stream_server.cpp
index 8408ac965d..542c8edffa 100644
--- a/asio/src/examples/cpp11/local/fd_passing_stream_server.cpp
+++ b/asio/src/examples/cpp11/local/fd_passing_stream_server.cpp
@@ -4,6 +4,7 @@
 //
 // Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 // Copyright (c) 2021 Heiko Hund (heiko at openvpn dot net)
+// Copyright (c) 2025 Pavlo Kleymonov (pkleymonov at qnx dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -22,6 +23,14 @@
 
 #if defined(ASIO_HAS_LOCAL_SOCKETS)
 
+#if defined(__QNX__)
+   #undef CMSG_ALIGN
+   #define CMSG_ALIGN(len) (((len) + sizeof (size_t) - 1) & (size_t) ~(sizeof (size_t) - 1))
+
+   #undef CMSG_SPACE
+   #define CMSG_SPACE(len) (CMSG_ALIGN (len) + CMSG_ALIGN (sizeof (struct cmsghdr)))
+#endif //defined(__QNX__)
+
 using asio::local::stream_protocol;
 
 class session
diff --git a/asio/src/tests/unit/ip/multicast.cpp b/asio/src/tests/unit/ip/multicast.cpp
index 2b6eddc4d2..a68dfa0d0d 100644
--- a/asio/src/tests/unit/ip/multicast.cpp
+++ b/asio/src/tests/unit/ip/multicast.cpp
@@ -3,6 +3,7 @@
 // ~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+// Copyright (c) 2025 Pavlo Kleymonov (pkleymonov at qnx dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -146,17 +147,20 @@ void test()
 #if (defined(__MACH__) && defined(__APPLE__)) \
   || defined(__FreeBSD__) \
   || defined(__NetBSD__) \
-  || defined(__OpenBSD__)
+  || defined(__OpenBSD__) \
+  || defined(__QNX__)
   const ip::address multicast_address_v6 = ip::make_address("ff02::1%lo0", ec);
 #else // (defined(__MACH__) && defined(__APPLE__))
       //   || defined(__FreeBSD__)
       //   || defined(__NetBSD__)
       //   || defined(__OpenBSD__)
+      //   || defined(__QNX__)
   const ip::address multicast_address_v6 = ip::make_address("ff01::1", ec);
 #endif // (defined(__MACH__) && defined(__APPLE__))
        //   || defined(__FreeBSD__)
        //   || defined(__NetBSD__)
        //   || defined(__OpenBSD__)
+       //   || defined(__QNX__)
   ASIO_CHECK(!have_v6 || !ec);
 
   // join_group class.
@@ -207,11 +211,11 @@ void test()
 
   if (have_v6)
   {
-#if defined(__hpux)
+#if defined(__hpux) || defined(__QNX__)
     ip::multicast::outbound_interface outbound_interface(if_nametoindex("lo0"));
 #else
     ip::multicast::outbound_interface outbound_interface(1);
-#endif
+#endif // defined(__hpux) || defined(__QNX__)
     sock_v6.set_option(outbound_interface, ec);
     ASIO_CHECK_MESSAGE(!ec, ec.value() << ", " << ec.message());
   }