diff --git a/include/shell/shell.h b/include/shell/shell.h
index 5edf2229945..d7316b283b4 100644
--- a/include/shell/shell.h
+++ b/include/shell/shell.h
@@ -374,6 +374,7 @@ struct shell_flags {
 	u32_t tx_rdy      :1;
 	u32_t mode_delete :1; /*!< Operation mode of backspace key */
 	u32_t history_exit:1; /*!< Request to exit history mode */
+	u32_t cmd_ctx	  :1; /*!< Shell is executing command */
 	u32_t last_nl     :8; /*!< Last received new line character */
 };
 
@@ -683,7 +684,10 @@ void shell_help(const struct shell *shell);
  * Pass command line to shell to execute.
  *
  * Note: This by no means makes any of the commands a stable interface, so
- * this function should only be used for debugging/diagnostic.
+ * 	 this function should only be used for debugging/diagnostic.
+ *
+ *	 This function must not be called from shell command context!
+
  *
  * @param[in] shell	Pointer to the shell instance. It can be NULL when
  *			the :option:`CONFIG_SHELL_BACKEND_DUMMY` option is
diff --git a/subsys/shell/shell.c b/subsys/shell/shell.c
index ca3501934c8..cccae2e69e3 100644
--- a/subsys/shell/shell.c
+++ b/subsys/shell/shell.c
@@ -42,6 +42,16 @@ static void cmd_buffer_clear(const struct shell *shell)
 	shell->ctx->cmd_buff_len = 0;
 }
 
+static void shell_internal_help_print(const struct shell *shell)
+{
+	if (!IS_ENABLED(CONFIG_SHELL_HELP)) {
+		return;
+	}
+
+	shell_help_cmd_print(shell);
+	shell_help_subcmd_print(shell);
+}
+
 /**
  * @brief Prints error message on wrong argument count.
  *	  Optionally, printing help on wrong argument count.
@@ -56,12 +66,12 @@ static int cmd_precheck(const struct shell *shell,
 			bool arg_cnt_ok)
 {
 	if (!arg_cnt_ok) {
-		shell_fprintf(shell, SHELL_ERROR,
-			      "%s: wrong parameter count\n",
-			      shell->ctx->active_cmd.syntax);
+		shell_internal_fprintf(shell, SHELL_ERROR,
+				       "%s: wrong parameter count\n",
+				       shell->ctx->active_cmd.syntax);
 
 		if (IS_ENABLED(CONFIG_SHELL_HELP_ON_WRONG_ARGUMENT_COUNT)) {
-			shell_help(shell);
+			shell_internal_help_print(shell);
 		}
 
 		return -EINVAL;
@@ -100,9 +110,10 @@ static void tab_item_print(const struct shell *shell, const char *option,
 	diff = longest_option - shell_strlen(option);
 
 	if (shell->ctx->vt100_ctx.printed_cmd++ % columns == 0) {
-		shell_fprintf(shell, SHELL_OPTION, "\n%s%s", tab, option);
+		shell_internal_fprintf(shell, SHELL_OPTION, "\n%s%s", tab,
+				       option);
 	} else {
-		shell_fprintf(shell, SHELL_OPTION, "%s", option);
+		shell_internal_fprintf(shell, SHELL_OPTION, "%s", option);
 	}
 
 	shell_op_cursor_horiz_move(shell, diff);
@@ -515,11 +526,11 @@ static int exec_cmd(const struct shell *shell, size_t argc, char **argv,
 			if (help_entry->help != shell->ctx->active_cmd.help) {
 				shell->ctx->active_cmd = *help_entry;
 			}
-			shell_help(shell);
+			shell_internal_help_print(shell);
 			return SHELL_CMD_HELP_PRINTED;
 		} else {
-			shell_fprintf(shell, SHELL_ERROR,
-				      SHELL_MSG_SPECIFY_SUBCOMMAND);
+			shell_internal_fprintf(shell, SHELL_ERROR,
+					       SHELL_MSG_SPECIFY_SUBCOMMAND);
 			return -ENOEXEC;
 		}
 	}
@@ -544,7 +555,15 @@ static int exec_cmd(const struct shell *shell, size_t argc, char **argv,
 	}
 
 	if (!ret_val) {
+		/* Unlock thread mutex in case command would like to borrow
+		 * shell context to other thread to avoid mutex deadlock.
+		 */
+		k_mutex_unlock(&shell->ctx->wr_mtx);
+		flag_cmd_ctx_set(shell, 1);
 		ret_val = shell->ctx->active_cmd.handler(shell, argc, argv);
+		flag_cmd_ctx_set(shell, 0);
+		/* Bring back mutex to shell thread. */
+		k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
 	}
 
 	return ret_val;
@@ -593,8 +612,9 @@ static int execute(const struct shell *shell)
 	}
 
 	if (quote != 0) {
-		shell_fprintf(shell, SHELL_ERROR, "not terminated: %c\n",
-			      quote);
+		shell_internal_fprintf(shell, SHELL_ERROR,
+				       "not terminated: %c\n",
+				       quote);
 		return -ENOEXEC;
 	}
 
@@ -612,12 +632,12 @@ static int execute(const struct shell *shell)
 			 */
 			if (help_entry.help) {
 				shell->ctx->active_cmd = help_entry;
-				shell_help(shell);
+				shell_internal_help_print(shell);
 				return SHELL_CMD_HELP_PRINTED;
 			}
 
-			shell_fprintf(shell, SHELL_ERROR,
-				      SHELL_MSG_SPECIFY_SUBCOMMAND);
+			shell_internal_fprintf(shell, SHELL_ERROR,
+					       SHELL_MSG_SPECIFY_SUBCOMMAND);
 			return -ENOEXEC;
 		}
 
@@ -648,8 +668,9 @@ static int execute(const struct shell *shell)
 
 		if ((cmd_idx == 0) || (p_static_entry == NULL)) {
 			if (cmd_lvl == 0) {
-				shell_error(shell, "%s%s", argv[0],
-					    SHELL_MSG_CMD_NOT_FOUND);
+				shell_internal_fprintf(shell, SHELL_ERROR,
+						       "%s%s\n", argv[0],
+						       SHELL_MSG_CMD_NOT_FOUND);
 				return -ENOEXEC;
 			}
 			break;
@@ -668,7 +689,8 @@ static int execute(const struct shell *shell)
 					 * a handler to avoid multiple function
 					 * calls.
 					 */
-					shell_fprintf(shell, SHELL_ERROR,
+					shell_internal_fprintf(shell,
+						SHELL_ERROR,
 						"Error: requested multiple"
 						" function executions\n");
 
@@ -1180,7 +1202,8 @@ void shell_thread(void *shell_handle, void *arg_log_backend,
 		k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
 
 		if (err != 0) {
-			shell_error(shell, "Shell thread error: %d", err);
+			shell_internal_fprintf(shell, SHELL_ERROR,
+					       "Shell thread error: %d", err);
 			return;
 		}
 
@@ -1307,48 +1330,36 @@ void shell_process(const struct shell *shell)
 			 internal.value);
 }
 
-
-
+/* This function mustn't be used from shell context to avoid deadlock.
+ * However it can be used in shell command handlers.
+ */
 void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
 		   const char *fmt, ...)
 {
 	__ASSERT_NO_MSG(shell);
 	__ASSERT(!k_is_in_isr(), "Thread context required.");
+	__ASSERT_NO_MSG((shell->ctx->internal.flags.cmd_ctx == 1) ||
+			(k_current_get() != shell->ctx->tid));
 	__ASSERT_NO_MSG(shell->ctx);
 	__ASSERT_NO_MSG(shell->fprintf_ctx);
 	__ASSERT_NO_MSG(fmt);
 
 	va_list args = { 0 };
 
-	if (k_current_get() != shell->ctx->tid) {
-		k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
+	k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
+	if (!flag_cmd_ctx_get(shell)) {
 		shell_cmd_line_erase(shell);
 	}
 
 	va_start(args, fmt);
-
-	if (IS_ENABLED(CONFIG_SHELL_VT100_COLORS) &&
-	    shell->ctx->internal.flags.use_colors &&
-	    (color != shell->ctx->vt100_ctx.col.col)) {
-		struct shell_vt100_colors col;
-
-		shell_vt100_colors_store(shell, &col);
-		shell_vt100_color_set(shell, color);
-
-		shell_fprintf_fmt(shell->fprintf_ctx, fmt, args);
-
-		shell_vt100_colors_restore(shell, &col);
-	} else {
-		shell_fprintf_fmt(shell->fprintf_ctx, fmt, args);
-	}
-
+	shell_internal_vfprintf(shell, color, fmt, args);
 	va_end(args);
 
-	if (k_current_get() != shell->ctx->tid) {
+	if (!flag_cmd_ctx_get(shell)) {
 		shell_print_prompt_and_cmd(shell);
-		transport_buffer_flush(shell);
-		k_mutex_unlock(&shell->ctx->wr_mtx);
 	}
+	transport_buffer_flush(shell);
+	k_mutex_unlock(&shell->ctx->wr_mtx);
 }
 
 int shell_prompt_change(const struct shell *shell, const char *prompt)
@@ -1366,19 +1377,15 @@ int shell_prompt_change(const struct shell *shell, const char *prompt)
 
 void shell_help(const struct shell *shell)
 {
-	__ASSERT_NO_MSG(shell);
-
-	if (!IS_ENABLED(CONFIG_SHELL_HELP)) {
-		return;
-	}
-
-	shell_help_cmd_print(shell);
-	shell_help_subcmd_print(shell);
+	k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
+	shell_internal_help_print(shell);
+	k_mutex_unlock(&shell->ctx->wr_mtx);
 }
 
 int shell_execute_cmd(const struct shell *shell, const char *cmd)
 {
 	u16_t cmd_len = shell_strlen(cmd);
+	int ret_val;
 
 	if (cmd == NULL) {
 		return -ENOEXEC;
@@ -1396,9 +1403,17 @@ int shell_execute_cmd(const struct shell *shell, const char *cmd)
 #endif
 	}
 
+	__ASSERT(shell->ctx->internal.flags.cmd_ctx == 0,
+						"Function cannot be called"
+						" from command context");
+
 	strcpy(shell->ctx->cmd_buff, cmd);
 	shell->ctx->cmd_buff_len = cmd_len;
 	shell->ctx->cmd_buff_pos = cmd_len;
 
-	return execute(shell);
+	k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
+	ret_val = execute(shell);
+	k_mutex_unlock(&shell->ctx->wr_mtx);
+
+	return ret_val;
 }
diff --git a/subsys/shell/shell_help.c b/subsys/shell/shell_help.c
index ed46e642410..fed9a0e173b 100644
--- a/subsys/shell/shell_help.c
+++ b/subsys/shell/shell_help.c
@@ -118,20 +118,20 @@ static void help_item_print(const struct shell *shell, const char *item_name,
 
 	if (!IS_ENABLED(CONFIG_NEWLIB_LIBC) && !IS_ENABLED(CONFIG_ARCH_POSIX)) {
 		/* print option name */
-		shell_fprintf(shell, SHELL_NORMAL, "%s%-*s%s:",
-			      tabulator,
-			      item_name_width, item_name,
-			      tabulator);
+		shell_internal_fprintf(shell, SHELL_NORMAL, "%s%-*s%s:",
+				       tabulator,
+				       item_name_width, item_name,
+				       tabulator);
 	} else {
 		u16_t tmp = item_name_width - strlen(item_name);
 		char space = ' ';
 
-		shell_fprintf(shell, SHELL_NORMAL, "%s%s", tabulator,
-			      item_name);
+		shell_internal_fprintf(shell, SHELL_NORMAL, "%s%s", tabulator,
+				       item_name);
 		for (u16_t i = 0; i < tmp; i++) {
 			shell_write(shell, &space, 1);
 		}
-		shell_fprintf(shell, SHELL_NORMAL, "%s:", tabulator);
+		shell_internal_fprintf(shell, SHELL_NORMAL, "%s:", tabulator);
 	}
 
 	if (item_help == NULL) {
@@ -176,7 +176,7 @@ void shell_help_subcmd_print(const struct shell *shell)
 		return;
 	}
 
-	shell_fprintf(shell, SHELL_NORMAL, "Subcommands:\n");
+	shell_internal_fprintf(shell, SHELL_NORMAL, "Subcommands:\n");
 
 	/* Printing subcommands and help string (if exists). */
 	cmd_idx = 0;
@@ -202,8 +202,8 @@ void shell_help_cmd_print(const struct shell *shell)
 	u16_t field_width = shell_strlen(shell->ctx->active_cmd.syntax) +
 							  shell_strlen(cmd_sep);
 
-	shell_fprintf(shell, SHELL_NORMAL, "%s%s",
-		      shell->ctx->active_cmd.syntax, cmd_sep);
+	shell_internal_fprintf(shell, SHELL_NORMAL, "%s%s",
+			       shell->ctx->active_cmd.syntax, cmd_sep);
 
 	formatted_text_print(shell, shell->ctx->active_cmd.help,
 			     field_width, false);
diff --git a/subsys/shell/shell_ops.c b/subsys/shell/shell_ops.c
index 181bc7af03d..75ef5a5777c 100644
--- a/subsys/shell/shell_ops.c
+++ b/subsys/shell/shell_ops.c
@@ -178,7 +178,7 @@ void shell_op_word_remove(const struct shell *shell)
 	/* Update display. */
 	shell_op_cursor_move(shell, -chars_to_delete);
 	cursor_save(shell);
-	shell_fprintf(shell, SHELL_NORMAL, "%s", str + 1);
+	shell_internal_fprintf(shell, SHELL_NORMAL, "%s", str + 1);
 	clear_eos(shell);
 	cursor_restore(shell);
 }
@@ -223,7 +223,7 @@ static void reprint_from_cursor(const struct shell *shell, u16_t diff,
 		clear_eos(shell);
 	}
 
-	shell_fprintf(shell, SHELL_NORMAL, "%s",
+	shell_internal_fprintf(shell, SHELL_NORMAL, "%s",
 		      &shell->ctx->cmd_buff[shell->ctx->cmd_buff_pos]);
 	shell->ctx->cmd_buff_pos = shell->ctx->cmd_buff_len;
 
@@ -336,21 +336,7 @@ void shell_cmd_line_erase(const struct shell *shell)
 
 static void print_prompt(const struct shell *shell)
 {
-	/* Below cannot be printed by shell_fprinf because it will cause
-	 * interrupt spin
-	 */
-	if (IS_ENABLED(CONFIG_SHELL_VT100_COLORS) &&
-	    shell->ctx->internal.flags.use_colors &&
-	    (SHELL_INFO != shell->ctx->vt100_ctx.col.col)) {
-		struct shell_vt100_colors col;
-
-		shell_vt100_colors_store(shell, &col);
-		shell_vt100_color_set(shell, SHELL_INFO);
-		shell_raw_fprintf(shell->fprintf_ctx, "%s", shell->ctx->prompt);
-		shell_vt100_colors_restore(shell, &col);
-	} else {
-		shell_raw_fprintf(shell->fprintf_ctx, "%s", shell->ctx->prompt);
-	}
+	shell_internal_fprintf(shell, SHELL_INFO, "%s", shell->ctx->prompt);
 }
 
 void shell_print_cmd(const struct shell *shell)
@@ -457,3 +443,40 @@ void shell_vt100_colors_restore(const struct shell *shell,
 	shell_vt100_color_set(shell, color->col);
 	vt100_bgcolor_set(shell, color->bgcol);
 }
+
+void shell_internal_vfprintf(const struct shell *shell,
+			     enum shell_vt100_color color, const char *fmt,
+			     va_list args)
+{
+	if (IS_ENABLED(CONFIG_SHELL_VT100_COLORS) &&
+	    shell->ctx->internal.flags.use_colors &&
+	    (color != shell->ctx->vt100_ctx.col.col)) {
+		struct shell_vt100_colors col;
+
+		shell_vt100_colors_store(shell, &col);
+		shell_vt100_color_set(shell, color);
+
+		shell_fprintf_fmt(shell->fprintf_ctx, fmt, args);
+
+		shell_vt100_colors_restore(shell, &col);
+	} else {
+		shell_fprintf_fmt(shell->fprintf_ctx, fmt, args);
+	}
+}
+
+void shell_internal_fprintf(const struct shell *shell,
+			    enum shell_vt100_color color,
+			    const char *fmt, ...)
+{
+	__ASSERT_NO_MSG(shell);
+	__ASSERT(!k_is_in_isr(), "Thread context required.");
+	__ASSERT_NO_MSG(shell->ctx);
+	__ASSERT_NO_MSG(shell->fprintf_ctx);
+	__ASSERT_NO_MSG(fmt);
+
+	va_list args = { 0 };
+
+	va_start(args, fmt);
+	shell_internal_vfprintf(shell, color, fmt, args);
+	va_end(args);
+}
diff --git a/subsys/shell/shell_ops.h b/subsys/shell/shell_ops.h
index 93baaa06123..06a5bac027a 100644
--- a/subsys/shell/shell_ops.h
+++ b/subsys/shell/shell_ops.h
@@ -134,6 +134,16 @@ static inline void flag_history_exit_set(const struct shell *shell, bool val)
 	shell->ctx->internal.flags.history_exit = val ? 1 : 0;
 }
 
+static inline bool flag_cmd_ctx_get(const struct shell *shell)
+{
+	return shell->ctx->internal.flags.cmd_ctx == 1 ? true : false;
+}
+
+static inline void flag_cmd_ctx_set(const struct shell *shell, bool val)
+{
+	shell->ctx->internal.flags.cmd_ctx = val ? 1 : 0;
+}
+
 static inline u8_t flag_last_nl_get(const struct shell *shell)
 {
 	return shell->ctx->internal.flags.last_nl;
@@ -246,6 +256,17 @@ static inline void shell_vt100_colors_store(const struct shell *shell,
 void shell_vt100_colors_restore(const struct shell *shell,
 				const struct shell_vt100_colors *color);
 
+/* This function can be called only within shell thread but not from command
+ * handlers.
+ */
+void shell_internal_fprintf(const struct shell *shell,
+			    enum shell_vt100_color color,
+			    const char *fmt, ...);
+
+void shell_internal_vfprintf(const struct shell *shell,
+			     enum shell_vt100_color color, const char *fmt,
+			     va_list args);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/subsys/shell/shell_wildcard.c b/subsys/shell/shell_wildcard.c
index b3a6da5b2e2..59bf52457e4 100644
--- a/subsys/shell/shell_wildcard.c
+++ b/subsys/shell/shell_wildcard.c
@@ -8,7 +8,7 @@
 #include <fnmatch.h>
 #include "shell_wildcard.h"
 #include "shell_utils.h"
-
+#include "shell_ops.h"
 
 static void subcmd_get(const struct shell_cmd_entry *cmd,
 		       size_t idx, const struct shell_static_entry **entry,
@@ -109,7 +109,7 @@ static enum shell_wildcard_status commands_expand(const struct shell *shell,
 					      &shell->ctx->cmd_tmp_buff_len,
 					      p_static_entry->syntax, pattern);
 			if (ret_val == SHELL_WILDCARD_CMD_MISSING_SPACE) {
-				shell_fprintf(shell,
+				shell_internal_fprintf(shell,
 					      SHELL_WARNING,
 					      "Command buffer is too short to"
 					      " expand all commands matching"