diff --git a/src/lib/libpthread.js b/src/lib/libpthread.js
index 67a7b173a0f70..7b5cf83889bfa 100644
--- a/src/lib/libpthread.js
+++ b/src/lib/libpthread.js
@@ -270,83 +270,84 @@ var LibraryPThread = {
       PThread.tlsInitFunctions.forEach((f) => f());
     },
     // Loads the WebAssembly module into the given Worker.
-    // onFinishedLoading: A callback function that will be called once all of
-    //                    the workers have been initialized and are
-    //                    ready to host pthreads.
-    loadWasmModuleToWorker: (worker) => new Promise((onFinishedLoading) => {
-      worker.onmessage = (e) => {
-        var d = e['data'];
-        var cmd = d.cmd;
-#if PTHREADS_DEBUG
-        dbg(`main thread: received message '${cmd}' from worker. ${d}`);
-#endif
-
-        // If this message is intended to a recipient that is not the main
-        // thread, forward it to the target thread.
-        if (d.targetThread && d.targetThread != _pthread_self()) {
-          var targetWorker = PThread.pthreads[d.targetThread];
-          if (targetWorker) {
-            targetWorker.postMessage(d, d.transferList);
-          } else {
-            err(`worker sent message (${cmd}) to pthread (${d.targetThread}) that no longer exists`);
+    // @returns: A promise the resolves once the worker has loaded the wasm module
+    //           and is ready to run a pthread.
+    loadWasmModuleToWorker: (worker) => {
+      worker.loaded = new Promise((onFinishedLoading) => {
+        worker.onmessage = (e) => {
+          var d = e['data'];
+          var cmd = d.cmd;
+  #if PTHREADS_DEBUG
+          dbg(`main thread: received message '${cmd}' from worker. ${d}`);
+  #endif
+
+          // If this message is intended to a recipient that is not the main
+          // thread, forward it to the target thread.
+          if (d.targetThread && d.targetThread != _pthread_self()) {
+            var targetWorker = PThread.pthreads[d.targetThread];
+            if (targetWorker) {
+              targetWorker.postMessage(d, d.transferList);
+            } else {
+              err(`worker sent message (${cmd}) to pthread (${d.targetThread}) that no longer exists`);
+            }
+            return;
           }
-          return;
-        }
 
-        if (d === 'setimmediate') {
-          // Worker wants to postMessage() to itself to implement setImmediate()
-          // emulation.
-          worker.postMessage(d);
-          return;
-        }
+          if (d === 'setimmediate') {
+            // Worker wants to postMessage() to itself to implement setImmediate()
+            // emulation.
+            worker.postMessage(d);
+            return;
+          }
 
-        switch (cmd) {
-          case {{{ CMD_CHECK_MAILBOX }}}:
-            checkMailbox();
-            break;
-          case {{{ CMD_SPAWN_THREAD }}}:
-            spawnThread(d);
-            break;
-          case {{{ CMD_CLEANUP_THREAD }}}:
-            // cleanupThread needs to be run via callUserCallback since it calls
-            // back into user code to free thread data. Without this it's possible
-            // the unwind or ExitStatus exception could escape here.
-            callUserCallback(() => cleanupThread(d.thread));
-            break;
+          switch (cmd) {
+            case {{{ CMD_CHECK_MAILBOX }}}:
+              checkMailbox();
+              break;
+            case {{{ CMD_SPAWN_THREAD }}}:
+              spawnThread(d);
+              break;
+            case {{{ CMD_CLEANUP_THREAD }}}:
+              // cleanupThread needs to be run via callUserCallback since it calls
+              // back into user code to free thread data. Without this it's possible
+              // the unwind or ExitStatus exception could escape here.
+              callUserCallback(() => cleanupThread(d.thread));
+              break;
 #if MAIN_MODULE
-          case {{{ CMD_MARK_AS_FINISHED }}}:
-            markAsFinished(d.thread);
-            break;
+            case {{{ CMD_MARK_AS_FINISHED }}}:
+              markAsFinished(d.thread);
+              break;
 #endif
-          case {{{ CMD_LOADED }}}:
+            case {{{ CMD_LOADED }}}:
 #if ENVIRONMENT_MAY_BE_NODE
-            if (ENVIRONMENT_IS_NODE && !worker.strongref) {
-              // Once worker is loaded & idle, mark it as weakly referenced,
-              // so that mere existence of a Worker in the pool does not prevent
-              // Node.js from exiting the app.
-              worker.unref();
-            }
-#endif
-            onFinishedLoading(worker);
-            break;
+              if (ENVIRONMENT_IS_NODE && !worker.strongref) {
+                // Once worker is loaded & idle, mark it as weakly referenced,
+                // so that mere existence of a Worker in the pool does not prevent
+                // Node.js from exiting the app.
+                worker.unref();
+              }
+#endif
+              onFinishedLoading();
+              break;
 #if ENVIRONMENT_MAY_BE_NODE
-          case {{{ CMD_UNCAUGHT_EXN }}}:
-            // Message handler for Node.js specific out-of-order behavior:
-            // https://github.com/nodejs/node/issues/59617
-            // A pthread sent an uncaught exception event. Re-raise it on the main thread.
-            worker.onerror(d.error);
-            break;
-#endif
-          case {{{ CMD_CALL_HANDLER }}}:
-            Module[d.handler](...d.args);
-            break;
-          default:
-            // The received message looks like something that should be handled by this message
-            // handler, (since there is a e.data.cmd field present), but is not one of the
-            // recognized commands:
-            if (cmd) err(`worker sent an unknown command ${cmd}`);
-        }
-      };
+            case {{{ CMD_UNCAUGHT_EXN }}}:
+              // Message handler for Node.js specific out-of-order behavior:
+              // https://github.com/nodejs/node/issues/59617
+              // A pthread sent an uncaught exception event. Re-raise it on the main thread.
+              worker.onerror(d.error);
+              break;
+#endif
+            case {{{ CMD_CALL_HANDLER }}}:
+              Module[d.handler](...d.args);
+              break;
+            default:
+              // The received message looks like something that should be handled by this message
+              // handler, (since there is a e.data.cmd field present), but is not one of the
+              // recognized commands:
+              if (cmd) err(`worker sent an unknown command ${cmd}`);
+          }
+        };
+      });
 
       worker.onerror = (e) => {
         var message = 'worker sent an error!';
@@ -443,7 +444,9 @@ var LibraryPThread = {
         'workerID': worker.workerID,
 #endif
       });
-    }),
+
+      return worker.loaded;
+    },
 
 #if PTHREAD_POOL_SIZE
     async loadWasmModuleToAllWorkers() {
@@ -730,7 +733,11 @@ var LibraryPThread = {
 #endif
     // Ask the worker to start executing its pthread entry point function.
     worker.postMessage(msg, threadParams.transferList);
+#if ASYNCIFY
+    return worker.loaded;
+#else
     return 0;
+#endif
   },
 
   _emscripten_init_main_thread_js: (tb) => {
@@ -775,6 +782,11 @@ var LibraryPThread = {
   // allocations from __pthread_create_js we could also remove this.
   __pthread_create_js__noleakcheck: true,
 #endif
+  // Pthread creation is async when possible.  This allows us to return to the
+  // event loop and wait for the Worker to be created.
+  // This is needed in browsers where synchronous worker creation is still not
+  // possible: <BUG_LINK>
+  __pthread_create_js__async: 'auto',
   __pthread_create_js__deps: ['$spawnThread', '$pthreadCreateProxied',
     'emscripten_has_threading_support',
 #if OFFSCREENCANVAS_SUPPORT
diff --git a/src/postamble.js b/src/postamble.js
index 37a06dc690940..4336c32e25011 100644
--- a/src/postamble.js
+++ b/src/postamble.js
@@ -78,7 +78,7 @@ var mainArgs = undefined;
     var ret = entryFunction(argc, {{{ to64('argv') }}});
 #endif // STANDALONE_WASM
 
-#if ASYNCIFY == 2 && !PROXY_TO_PTHREAD
+#if ASYNCIFY == 2
     // The current spec of JSPI returns a promise only if the function suspends
     // and a plain value otherwise. This will likely change:
     // https://github.com/WebAssembly/js-promise-integration/issues/11
diff --git a/test/decorators.py b/test/decorators.py
index 78e14857c41cd..9a54c8a937120 100644
--- a/test/decorators.py
+++ b/test/decorators.py
@@ -603,6 +603,47 @@ def metafunc(self, mode, *args, **kwargs):
   return metafunc
 
 
+def with_asyncify_and_jspi(func):
+  assert callable(func)
+
+  @wraps(func)
+  def metafunc(self, jspi, *args, **kwargs):
+    if self.get_setting('WASM_ESM_INTEGRATION'):
+      self.skipTest('WASM_ESM_INTEGRATION is not compatible with ASYNCIFY')
+    if jspi:
+      self.set_setting('JSPI')
+      self.require_jspi()
+    else:
+      self.set_setting('ASYNCIFY')
+    return func(self, *args, **kwargs)
+
+  parameterize(metafunc, {'': (False,),
+                          'jspi': (True,)})
+  return metafunc
+
+
+def also_with_asyncify_and_jspi(func):
+  assert callable(func)
+
+  @wraps(func)
+  def metafunc(self, asyncify, *args, **kwargs):
+    if asyncify and self.get_setting('WASM_ESM_INTEGRATION'):
+      self.skipTest('WASM_ESM_INTEGRATION is not compatible with ASYNCIFY')
+    if asyncify == 2:
+      self.set_setting('JSPI')
+      self.require_jspi()
+    elif asyncify == 1:
+      self.set_setting('ASYNCIFY')
+    else:
+      assert asyncify == 0
+    return func(self, *args, **kwargs)
+
+  parameterize(metafunc, {'': (0,),
+                          'asyncify': (1,),
+                          'jspi': (2,)})
+  return metafunc
+
+
 def parameterize(func, parameters):
   """Add additional parameterization to a test function.
 
diff --git a/test/test_browser.py b/test/test_browser.py
index c3fe8de49d17a..3337ee3a04fcc 100644
--- a/test/test_browser.py
+++ b/test/test_browser.py
@@ -48,6 +48,7 @@
 )
 from decorators import (
   also_with_asan,
+  also_with_asyncify_and_jspi,
   also_with_fetch_streaming,
   also_with_minimal_runtime,
   also_with_pthreads,
@@ -66,6 +67,7 @@
   skip_if,
   skip_if_simple,
   with_all_sjlj,
+  with_asyncify_and_jspi,
 )
 
 from tools import ports, shared, utils
@@ -3666,6 +3668,10 @@ def test_pthread_pool_size_strict(self):
                expected='abort:Assertion failed: thrd_create(&t4, thread_main, NULL) == thrd_success',
                cflags=['-g2', '-pthread', '-sPTHREAD_POOL_SIZE=3', '-sPTHREAD_POOL_SIZE_STRICT=2'])
 
+  @with_asyncify_and_jspi
+  def test_pthread_asyncify(self):
+    self.btest_exit('pthread/test_pthread_printf.c', cflags=['-pthread'])
+
   def test_pthread_in_pthread_pool_size_strict(self):
     # Check that it fails when there's a pthread creating another pthread.
     self.btest_exit('pthread/test_pthread_create_pthread.c', cflags=['-g2', '-pthread', '-sPTHREAD_POOL_SIZE=2', '-sPTHREAD_POOL_SIZE_STRICT=2'])
@@ -3681,8 +3687,11 @@ def test_pthread_atomics(self, args):
     self.btest_exit('pthread/test_pthread_atomics.c', cflags=['-O3', '-pthread', '-sPTHREAD_POOL_SIZE=8', '-g1'] + args)
 
   # Test 64-bit atomics.
+  @also_with_asyncify_and_jspi
   def test_pthread_64bit_atomics(self):
-    self.btest_exit('pthread/test_pthread_64bit_atomics.c', cflags=['-O3', '-pthread', '-sPTHREAD_POOL_SIZE=8'])
+    if not self.get_setting('JSPI') and not self.get_setting('ASYNCIFY'):
+      self.set_setting('PTHREAD_POOL_SIZE', 8)
+    self.btest_exit('pthread/test_pthread_64bit_atomics.c', cflags=['-O3', '-pthread'])
 
   # Test 64-bit C++11 atomics.
   @also_with_pthreads
diff --git a/test/test_core.py b/test/test_core.py
index 1c437d8149c01..47a8e68db0db7 100644
--- a/test/test_core.py
+++ b/test/test_core.py
@@ -40,6 +40,7 @@
 )
 from decorators import (
   all_engines,
+  also_with_asyncify_and_jspi,
   also_with_minimal_runtime,
   also_with_modularize,
   also_with_nodefs,
@@ -76,6 +77,7 @@
   with_all_eh_sjlj,
   with_all_fs,
   with_all_sjlj,
+  with_asyncify_and_jspi,
   with_env_modify,
 )
 
@@ -255,47 +257,6 @@ def decorated(self, dylink_reversed, *args, **kwargs):
 only_wasm2js = skip_if('only_wasm2js', lambda t: not t.is_wasm2js())
 
 
-def with_asyncify_and_jspi(func):
-  assert callable(func)
-
-  @wraps(func)
-  def metafunc(self, jspi, *args, **kwargs):
-    if self.get_setting('WASM_ESM_INTEGRATION'):
-      self.skipTest('WASM_ESM_INTEGRATION is not compatible with ASYNCIFY')
-    if jspi:
-      self.set_setting('JSPI')
-      self.require_jspi()
-    else:
-      self.set_setting('ASYNCIFY')
-    return func(self, *args, **kwargs)
-
-  parameterize(metafunc, {'': (False,),
-                          'jspi': (True,)})
-  return metafunc
-
-
-def also_with_asyncify_and_jspi(func):
-  assert callable(func)
-
-  @wraps(func)
-  def metafunc(self, asyncify, *args, **kwargs):
-    if asyncify and self.get_setting('WASM_ESM_INTEGRATION'):
-      self.skipTest('WASM_ESM_INTEGRATION is not compatible with ASYNCIFY')
-    if asyncify == 2:
-      self.set_setting('JSPI')
-      self.require_jspi()
-    elif asyncify == 1:
-      self.set_setting('ASYNCIFY')
-    else:
-      assert asyncify == 0
-    return func(self, *args, **kwargs)
-
-  parameterize(metafunc, {'': (0,),
-                          'asyncify': (1,),
-                          'jspi': (2,)})
-  return metafunc
-
-
 def also_with_wasm_workers(func):
   assert callable(func)
 
diff --git a/tools/link.py b/tools/link.py
index 3d3d838da3733..c525cb6d3e038 100644
--- a/tools/link.py
+++ b/tools/link.py
@@ -64,6 +64,7 @@
 DEFAULT_ASYNCIFY_EXPORTS = [
   'main',
   '__main_argc_argv',
+  '_emscripten_proxy_main',
 ]
 
 VALID_ENVIRONMENTS = {'web', 'webview', 'worker', 'node', 'shell', 'worklet'}
@@ -1694,6 +1695,14 @@ def limit_incoming_module_api():
     settings.REQUIRED_EXPORTS += ['setThrew']
 
   if settings.ASYNCIFY:
+    # Warn against using PTHREAD_POOL_SIZE with ASYNCIFY, since there should be no need for it.
+    if 'PTHREAD_POOL_SIZE' in user_settings:
+      diagnostics.warning('emcc', 'PTHREAD_POOL_SIZE should not be needed under ASYNCIFY')
+    # PTHREAD_POOL_SIZE_STRICT is completely ignored since the warning/error it controls
+    # does not make sense with ASYNCIFY
+    if 'PTHREAD_POOL_SIZE_STRICT' in user_settings:
+      diagnostics.warning('unused-command-line-argument', 'PTHREAD_POOL_SIZE_STRICT is ignored under ASYNCIFY')
+    settings.PTHREAD_POOL_SIZE_STRICT = 0
     if not settings.ASYNCIFY_IGNORE_INDIRECT:
       # if we are not ignoring indirect calls, then we must treat invoke_* as if
       # they are indirect calls, since that is what they do - we can't see their