diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 67074d6..2c1bccb 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -48,6 +48,7 @@
     md5.c
     memory_buffer_alloc.c
     mps/reader.c
+    mps/trace.o
     nist_kw.c
     oid.c
     padlock.c
diff --git a/library/Makefile b/library/Makefile
index a67160c..0fb6eeb 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -105,6 +105,7 @@
 	     md5.o \
 	     memory_buffer_alloc.o \
              mps/reader.o \
+             mps/trace.o \
 	     nist_kw.o \
 	     oid.o \
 	     padlock.o \
diff --git a/library/mps/reader.c b/library/mps/reader.c
index 5c75c47..791b8bd 100644
--- a/library/mps/reader.c
+++ b/library/mps/reader.c
@@ -30,6 +30,10 @@
 #define inline __inline
 #endif
 
+#if defined(MBEDTLS_MPS_TRACE)
+static int trace_id = TRACE_BIT_READER;
+#endif /* MBEDTLS_MPS_TRACE */
+
 /*
  * GENERAL NOTE ON CODING STYLE
  *
diff --git a/library/mps/trace.c b/library/mps/trace.c
new file mode 100644
index 0000000..61965dc
--- /dev/null
+++ b/library/mps/trace.c
@@ -0,0 +1,122 @@
+/*
+ *  Message Processing Stack, Trace module
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of Mbed TLS (https://tls.mbed.org)
+ */
+
+#include "common.h"
+
+#if defined(MBEDTLS_MPS_TRACE)
+
+#include "trace.h"
+#include <stdarg.h>
+
+static int trace_depth_ = 0;
+
+#define color_default  "\x1B[0m"
+#define color_red      "\x1B[1;31m"
+#define color_green    "\x1B[1;32m"
+#define color_yellow   "\x1B[1;33m"
+#define color_blue     "\x1B[1;34m"
+#define color_magenta  "\x1B[1;35m"
+#define color_cyan     "\x1B[1;36m"
+#define color_white    "\x1B[1;37m"
+
+static char const * colors[] =
+{
+    color_default,
+    color_green,
+    color_yellow,
+    color_magenta,
+    color_cyan,
+    color_blue,
+    color_white
+};
+
+#define MPS_TRACE_BUF_SIZE 100
+
+void trace_print_msg( int id, int line, const char *format, ... )
+{
+    int ret;
+    char str[MPS_TRACE_BUF_SIZE];
+    va_list argp;
+    va_start( argp, format );
+    ret = mbedtls_vsnprintf( str, MPS_TRACE_BUF_SIZE, format, argp );
+    va_end( argp );
+
+    if( ret >= 0 && ret < MPS_TRACE_BUF_SIZE )
+    {
+        str[ret] = '\0';
+        mbedtls_printf( "[%d|L%d]: %s\n", id, line, str );
+    }
+}
+
+int trace_get_depth()
+{
+    return trace_depth_;
+}
+void trace_dec_depth()
+{
+    trace_depth_--;
+}
+void trace_inc_depth()
+{
+    trace_depth_++;
+}
+
+void trace_color( int id )
+{
+    if( id > (int) ( sizeof( colors ) / sizeof( *colors ) ) )
+        return;
+    printf( "%s", colors[ id ] );
+}
+
+void trace_indent( int level, trace_type ty )
+{
+    if( level > 0 )
+    {
+        while( --level )
+            printf( "|  " );
+
+        printf( "|  " );
+    }
+
+    switch( ty )
+    {
+        case trace_comment:
+            mbedtls_printf( "@ " );
+            break;
+
+        case trace_call:
+            mbedtls_printf( "+--> " );
+            break;
+
+        case trace_error:
+            mbedtls_printf( "E " );
+            break;
+
+        case trace_return:
+            mbedtls_printf( "< " );
+            break;
+
+        default:
+            break;
+    }
+}
+
+#endif /* MBEDTLS_MPS_TRACE */
diff --git a/library/mps/trace.h b/library/mps/trace.h
index 1ce079d..b1da7ed 100644
--- a/library/mps/trace.h
+++ b/library/mps/trace.h
@@ -28,15 +28,146 @@
 
 #include "common.h"
 
+#include "../common.h"
+
+#include "trace.h"
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#define mbedtls_printf    printf
+#define mbedtls_vsnprintf vsnprintf
+#endif /* MBEDTLS_PLATFORM_C */
+
 #if defined(MBEDTLS_MPS_TRACE)
 
-#error "MPS tracing module not yet implemented"
+/*
+ * Adapt this to enable/disable tracing output
+ * from the various layers of the MPS.
+ */
+
+#define TRACE_ENABLE_LAYER_1
+#define TRACE_ENABLE_LAYER_2
+#define TRACE_ENABLE_LAYER_3
+#define TRACE_ENABLE_LAYER_4
+#define TRACE_ENABLE_READER
+#define TRACE_ENABLE_WRITER
+
+/*
+ * To use the existing trace module, only change
+ * TRACE_ENABLE_XXX above, but don't modify the
+ * rest of this file.
+ */
+
+typedef enum
+{
+    trace_comment,
+    trace_call,
+    trace_error,
+    trace_return
+} trace_type;
+
+#define TRACE_BIT_LAYER_1 1
+#define TRACE_BIT_LAYER_2 2
+#define TRACE_BIT_LAYER_3 3
+#define TRACE_BIT_LAYER_4 4
+#define TRACE_BIT_WRITER  5
+#define TRACE_BIT_READER  6
+
+#if defined(TRACE_ENABLE_LAYER_1)
+#define TRACE_MASK_LAYER_1 (1u << TRACE_BIT_LAYER_1 )
+#else
+#define TRACE_MASK_LAYER_1 0
+#endif
+
+#if defined(TRACE_ENABLE_LAYER_2)
+#define TRACE_MASK_LAYER_2 (1u << TRACE_BIT_LAYER_2 )
+#else
+#define TRACE_MASK_LAYER_2 0
+#endif
+
+#if defined(TRACE_ENABLE_LAYER_3)
+#define TRACE_MASK_LAYER_3 (1u << TRACE_BIT_LAYER_3 )
+#else
+#define TRACE_MASK_LAYER_3 0
+#endif
+
+#if defined(TRACE_ENABLE_LAYER_4)
+#define TRACE_MASK_LAYER_4 (1u << TRACE_BIT_LAYER_4 )
+#else
+#define TRACE_MASK_LAYER_4 0
+#endif
+
+#if defined(TRACE_ENABLE_READER)
+#define TRACE_MASK_READER (1u << TRACE_BIT_READER )
+#else
+#define TRACE_MASK_READER 0
+#endif
+
+#if defined(TRACE_ENABLE_WRITER)
+#define TRACE_MASK_WRITER (1u << TRACE_BIT_WRITER )
+#else
+#define TRACE_MASK_WRITER 0
+#endif
+
+#define TRACE_MASK ( TRACE_MASK_LAYER_1 |           \
+                     TRACE_MASK_LAYER_2 |           \
+                     TRACE_MASK_LAYER_3 |           \
+                     TRACE_MASK_LAYER_4 |           \
+                     TRACE_MASK_READER  |           \
+                     TRACE_MASK_WRITER )
+
+/* We have to avoid globals because E-ACSL chokes on them...
+ * Wrap everything in stub functions. */
+int  trace_get_depth( void );
+void trace_inc_depth( void );
+void trace_dec_depth( void );
+
+void trace_color( int id );
+void trace_indent( int level, trace_type ty );
+
+void trace_print_msg( int id, int line, const char *format, ... );
+
+#define TRACE( type, ... )                                  \
+    do {                                                    \
+        if( ! ( TRACE_MASK & ( 1u << trace_id ) ) )         \
+            break;                                          \
+        trace_indent( trace_get_depth(), type );            \
+        trace_color( trace_id );                            \
+        trace_print_msg( trace_id, __LINE__, __VA_ARGS__ ); \
+        trace_color( 0 );                                   \
+    } while( 0 )
+
+#define TRACE_INIT( ... )                                   \
+    do {                                                    \
+        if( ! ( TRACE_MASK & ( 1u << trace_id ) ) )         \
+            break;                                          \
+        TRACE( trace_call, __VA_ARGS__ );                   \
+        trace_inc_depth();                                  \
+    } while( 0 )
+
+#define TRACE_END( val )                                    \
+    do {                                                    \
+        if( ! ( TRACE_MASK & ( 1u << trace_id ) ) )         \
+            break;                                          \
+        TRACE( trace_return, "%d (-%#04x)",                 \
+               (int) (val), -((unsigned)(val)) );           \
+        trace_dec_depth();                                  \
+    } while( 0 )
+
+#define RETURN( val )                           \
+    do {                                        \
+        /* Breaks tail recursion. */            \
+        int ret__ = val;                        \
+        TRACE_END( ret__ );                     \
+        return( ret__ );                        \
+    } while( 0 )
 
 #else /* MBEDTLS_MPS_TRACE */
 
-#define TRACE( type, fmt, ... ) do { } while( 0 )
-#define TRACE_INIT( fmt, ... )  do { } while( 0 )
-#define TRACE_END               do { } while( 0 )
+#define TRACE( type, ... ) do { } while( 0 )
+#define TRACE_INIT( ... )  do { } while( 0 )
+#define TRACE_END          do { } while( 0 )
 
 #define RETURN( val ) return( val );