diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index f556c0f..99c12cd 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -113,6 +113,120 @@
     return( 0 );
 }
 
+#if defined(MBEDTLS_SSL_ALPN)
+/*
+ * ssl_tls13_write_alpn_ext( ) structure:
+ *
+ * opaque ProtocolName<1..2^8-1>;
+ *
+ * struct {
+ *     ProtocolName protocol_name_list<2..2^16-1>
+ * } ProtocolNameList;
+ *
+ */
+static int ssl_tls13_write_alpn_ext( mbedtls_ssl_context *ssl,
+                               unsigned char *buf,
+                               const unsigned char *end,
+                               size_t *olen )
+{
+    unsigned char *p = buf;
+    size_t alpnlen = 0;
+    const char **cur;
+
+    *olen = 0;
+
+    if( ssl->conf->alpn_list == NULL )
+        return( 0 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding alpn extension" ) );
+
+    for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ )
+        alpnlen += strlen( *cur ) + 1;
+
+    MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 + alpnlen );
+
+    MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_ALPN, p, 0 );
+    p += 2;
+
+    /*
+     * opaque ProtocolName<1..2^8-1>;
+     *
+     * struct {
+     *     ProtocolName protocol_name_list<2..2^16-1>
+     * } ProtocolNameList;
+     */
+
+    /* Skip writing extension and list length for now */
+    p += 4;
+
+    for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ )
+    {
+        /*
+         * mbedtls_ssl_conf_set_alpn_protocols() checked that the length of
+         * protocol names is less than 255.
+         */
+        *p = (unsigned char)strlen( *cur );
+        memcpy( p + 1, *cur, *p );
+        p += 1 + *p;
+    }
+
+    *olen = p - buf;
+
+    /* List length = olen - 2 (ext_type) - 2 (ext_len) - 2 (list_len) */
+    MBEDTLS_PUT_UINT16_BE( *olen - 6, buf, 4 );
+
+    /* Extension length = olen - 2 (ext_type) - 2 (ext_len) */
+    MBEDTLS_PUT_UINT16_BE( *olen - 4, buf, 2 );
+
+    return( 0 );
+}
+
+static int ssl_tls13_parse_alpn_ext( mbedtls_ssl_context *ssl,
+                               const unsigned char *buf, size_t len )
+{
+    size_t list_len, name_len;
+    const unsigned char *p = buf;
+    const unsigned char *end = buf + len;
+
+    /* If we didn't send it, the server shouldn't send it */
+    if( ssl->conf->alpn_list == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    /*
+     * opaque ProtocolName<1..2^8-1>;
+     *
+     * struct {
+     *     ProtocolName protocol_name_list<2..2^16-1>
+     * } ProtocolNameList;
+     *
+     * the "ProtocolNameList" MUST contain exactly one "ProtocolName"
+     */
+
+    /* Min length is 2 ( list_len ) + 1 ( name_len ) + 1 ( name ) */
+    MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 4 );
+
+    list_len = MBEDTLS_GET_UINT16_BE( p, 0 );
+    p += 2;
+    MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_len );
+
+    name_len = *p++;
+    MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, list_len - 1 );
+
+    /* Check that the server chosen protocol was in our list and save it */
+    for ( const char **alpn = ssl->conf->alpn_list; *alpn != NULL; alpn++ )
+    {
+        if( name_len == strlen( *alpn ) &&
+            memcmp( buf + 3, *alpn, name_len ) == 0 )
+        {
+            ssl->alpn_chosen = *alpn;
+            return( 0 );
+        }
+    }
+
+    return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+}
+#endif /* MBEDTLS_SSL_ALPN */
+
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
 
 static int ssl_tls13_reset_key_share( mbedtls_ssl_context *ssl )
@@ -753,6 +867,13 @@
         return( ret );
     p += output_len;
 
+#if defined(MBEDTLS_SSL_ALPN)
+    ssl_tls13_write_alpn_ext( ssl, p, end, &output_len );
+    if( ret != 0 )
+        return( ret );
+    p += output_len;
+#endif /* MBEDTLS_SSL_ALPN */
+
 #if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
 
     /*
@@ -1622,6 +1743,17 @@
                 MBEDTLS_SSL_DEBUG_MSG( 3, ( "found extensions supported groups" ) );
                 break;
 
+#if defined(MBEDTLS_SSL_ALPN)
+            case MBEDTLS_TLS_EXT_ALPN:
+                MBEDTLS_SSL_DEBUG_MSG( 3, ( "found alpn extension" ) );
+
+                if( ( ret = ssl_tls13_parse_alpn_ext( ssl, p, (size_t)extension_data_len ) ) != 0 )
+                {
+                    return( ret );
+                }
+
+                break;
+#endif /* MBEDTLS_SSL_ALPN */
             default:
                 MBEDTLS_SSL_DEBUG_MSG(
                     3, ( "unsupported extension found: %u ", extension_type) );