diff --git a/testing/mochitest/runtests.py b/testing/mochitest/runtests.py
index 983f9f84c086..cb82ac0f7b45 100644
--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -1395,7 +1395,11 @@ class MochitestDesktop(object):
         serverOptions["isWin"] = mozinfo.isWin
         serverOptions["proxyPort"] = options.http3ServerPort
         env = test_environment(xrePath=options.xrePath, log=self.log)
-        self.http3Server = Http3Server(serverOptions, env, self.log)
+        serverEnv = env.copy()
+        serverLog = env.get("MOZHTTP3_SERVER_LOG")
+        if serverLog is not None:
+            serverEnv["RUST_LOG"] = serverLog
+        self.http3Server = Http3Server(serverOptions, serverEnv, self.log)
         self.http3Server.start()
 
         port = self.http3Server.ports().get("MOZHTTP3_PORT_PROXY")
diff --git a/testing/mozbase/mozserve/mozserve/servers.py b/testing/mozbase/mozserve/mozserve/servers.py
index 5484b32cfe5c..5a9f9117e7eb 100644
--- a/testing/mozbase/mozserve/mozserve/servers.py
+++ b/testing/mozbase/mozserve/mozserve/servers.py
@@ -11,6 +11,7 @@ import time
 from argparse import Namespace
 from contextlib import contextmanager
 from subprocess import PIPE, Popen
+from threading import Thread
 
 
 @contextmanager
@@ -52,6 +53,8 @@ class Http3Server(object):
         self._proxyPort = -1
         if options.get("proxyPort"):
             self._proxyPort = options["proxyPort"]
+        self.outthread = None
+        self.errthread = None
 
     def ports(self):
         return self._ports
@@ -59,6 +62,17 @@ class Http3Server(object):
     def echConfig(self):
         return self._echConfig
 
+    def read_streams(self, name, proc, pipe):
+        while True:
+            line = pipe.readline()
+            output = "stdout" if pipe == proc.stdout else "stderr"
+            if line:
+                self._log.info("server: %s [%s] %s" % (name, output, line))
+
+            # Check if process is dead
+            if proc.poll() is not None:
+                break
+
     def start(self):
         if not os.path.exists(self._http3ServerPath):
             raise Exception("Http3 server not found at %s" % self._http3ServerPath)
@@ -107,6 +121,21 @@ class Http3Server(object):
                     self._ports["MOZHTTP3_PORT_PROXY"] = searchObj.group(4)
                     self._ports["MOZHTTP3_PORT_NO_RESPONSE"] = searchObj.group(5)
                     self._echConfig = searchObj.group(6)
+                name = "http3server"
+                t1 = Thread(
+                    target=self.read_streams,
+                    args=(name, process, process.stdout),
+                    daemon=True
+                )
+                t1.start()
+                t2 = Thread(
+                    target=self.read_streams,
+                    args=(name, process, process.stderr),
+                    daemon=True
+                )
+                t2.start()
+                self.outthread = t1
+                self.errthread = t2
         except OSError as e:
             # This occurs if the subprocess couldn't be started
             self._log.error("Could not run the http3 server: %s" % (str(e)))
@@ -129,17 +158,12 @@ class Http3Server(object):
                         self._log.info("Killing proc")
                         proc.kill()
                         break
-
-            def dumpOutput(fd, label):
-                firstTime = True
-                for msg in fd:
-                    if firstTime:
-                        firstTime = False
-                        self._log.info("Process %s" % label)
-                    self._log.info(msg)
-
-            dumpOutput(proc.stdout, "stdout")
-            dumpOutput(proc.stderr, "stderr")
+        if self.outthread is not None:
+            self.outthread.join()
+            del self.outthread
+        if self.errthread is not None:
+            self.errthread.join()
+            del self.errthread
         self._http3ServerProc = {}
 
 
diff --git a/testing/xpcshell/runxpcshelltests.py b/testing/xpcshell/runxpcshelltests.py
index 4bca8abdfb70..04dcb73f4697 100755
--- a/testing/xpcshell/runxpcshelltests.py
+++ b/testing/xpcshell/runxpcshelltests.py
@@ -1494,7 +1494,11 @@ class XPCShellTests(object):
         options["profilePath"] = dbPath
         options["isMochitest"] = False
         options["isWin"] = sys.platform == "win32"
-        self.http3Server = Http3Server(options, self.env, self.log)
+        serverEnv = self.env.copy()
+        serverLog = self.env.get("MOZHTTP3_SERVER_LOG")
+        if serverLog is not None:
+            serverEnv["RUST_LOG"] = serverLog
+        self.http3Server = Http3Server(options, serverEnv, self.log)
         self.http3Server.start()
         for key, value in self.http3Server.ports().items():
             self.env[key] = value