diff --git a/Marlin/src/HAL/TEENSY40_41/HAL.cpp b/Marlin/src/HAL/TEENSY40_41/HAL.cpp
index 1d02ab8575c3..4dd5c3678d78 100644
--- a/Marlin/src/HAL/TEENSY40_41/HAL.cpp
+++ b/Marlin/src/HAL/TEENSY40_41/HAL.cpp
@@ -39,9 +39,19 @@
 
 #define _IMPLEMENT_SERIAL(X) DefaultSerial##X MSerial##X(false, Serial##X)
 #define IMPLEMENT_SERIAL(X)  _IMPLEMENT_SERIAL(X)
-#if WITHIN(SERIAL_PORT, 0, 3)
+#if WITHIN(SERIAL_PORT, 0, 8)
   IMPLEMENT_SERIAL(SERIAL_PORT);
 #endif
+#ifdef SERIAL_PORT_2
+  #if WITHIN(SERIAL_PORT_2, 0, 8)
+    IMPLEMENT_SERIAL(SERIAL_PORT_2);
+  #endif
+#endif
+#ifdef SERIAL_PORT_3
+  #if WITHIN(SERIAL_PORT_3, 0, 8)
+    IMPLEMENT_SERIAL(SERIAL_PORT_3);
+  #endif
+#endif
 USBSerialType USBSerial(false, SerialUSB);
 
 // ------------------------
diff --git a/Marlin/src/HAL/TEENSY40_41/HAL.h b/Marlin/src/HAL/TEENSY40_41/HAL.h
index 84c584767705..ddda9be65f1a 100644
--- a/Marlin/src/HAL/TEENSY40_41/HAL.h
+++ b/Marlin/src/HAL/TEENSY40_41/HAL.h
@@ -80,7 +80,7 @@ extern USBSerialType USBSerial;
 #define MSERIAL(X) _MSERIAL(X)
 
 #if SERIAL_PORT == -1
-  #define MYSERIAL1 SerialUSB
+  #define MYSERIAL1 USBSerial
 #elif WITHIN(SERIAL_PORT, 0, 8)
   DECLARE_SERIAL(SERIAL_PORT);
   #define MYSERIAL1 MSERIAL(SERIAL_PORT)
@@ -90,16 +90,28 @@ extern USBSerialType USBSerial;
 
 #ifdef SERIAL_PORT_2
   #if SERIAL_PORT_2 == -1
-    #define MYSERIAL2 usbSerial
+    #define MYSERIAL2 USBSerial
   #elif SERIAL_PORT_2 == -2
     #define MYSERIAL2 ethernet.telnetClient
   #elif WITHIN(SERIAL_PORT_2, 0, 8)
+    DECLARE_SERIAL(SERIAL_PORT_2);
     #define MYSERIAL2 MSERIAL(SERIAL_PORT_2)
   #else
     #error "SERIAL_PORT_2 must be from 0 to 8, or -1 for Native USB, or -2 for Ethernet."
   #endif
 #endif
 
+#ifdef SERIAL_PORT_3
+  #if SERIAL_PORT_3 == -1
+    #define MYSERIAL3 USBSerial
+  #elif WITHIN(SERIAL_PORT_3, 0, 8)
+    DECLARE_SERIAL(SERIAL_PORT_3);
+    #define MYSERIAL3 MSERIAL(SERIAL_PORT_3)
+  #else
+    #error "SERIAL_PORT_3 must be from 0 to 8, or -1 for Native USB."
+  #endif
+#endif
+
 // ------------------------
 // Types
 // ------------------------