diff --git a/drivers/mbox/mbox_nrfx_ipc.c b/drivers/mbox/mbox_nrfx_ipc.c
index eac81666001..0d027889185 100644
--- a/drivers/mbox/mbox_nrfx_ipc.c
+++ b/drivers/mbox/mbox_nrfx_ipc.c
@@ -89,7 +89,7 @@ static int mbox_nrf_register_callback(const struct device *dev, uint32_t channel
 {
 	struct mbox_nrf_data *data = dev->data;
 
-	if (!is_rx_channel_valid(dev, channel)) {
+	if (channel >= IPC_CONF_NUM) {
 		return -EINVAL;
 	}
 
@@ -123,6 +123,10 @@ static int mbox_nrf_set_enabled(const struct device *dev, uint32_t channel, bool
 		return -EALREADY;
 	}
 
+	if (enable && (data->cb[channel] == NULL)) {
+		LOG_WRN("Enabling channel without a registered callback\n");
+	}
+
 	if (enable && data->enabled_mask == 0) {
 		irq_enable(DT_INST_IRQN(0));
 	}
diff --git a/include/drivers/mbox.h b/include/drivers/mbox.h
index b97d3987197..782dd1d33b9 100644
--- a/include/drivers/mbox.h
+++ b/include/drivers/mbox.h
@@ -405,7 +405,21 @@ static inline int z_impl_mbox_mtu_get(const struct device *dev)
 }
 
 /**
- * @brief Enable interrupts and callbacks for inbound channels.
+ * @brief Enable (disable) interrupts and callbacks for inbound channels.
+ *
+ * Enable interrupt for the channel when the parameter 'enable' is set to true.
+ * Disable it otherwise.
+ *
+ * Immediately after calling this function with 'enable' set to true, the
+ * channel is considered enabled and ready to receive signal and messages (even
+ * already pending), so the user must take care of installing a proper callback
+ * (if needed) using @a mbox_register_callback() on the channel before enabling
+ * it. For this reason it is recommended that all the channels are disabled at
+ * probe time.
+ *
+ * Enabling a channel for which there is no installed callback is considered
+ * undefined behavior (in general the driver must take care of gracefully
+ * handling spurious interrupts with no installed callback).
  *
  * @param channel Channel instance pointer.
  * @param enable Set to 0 to disable and to nonzero to enable.
diff --git a/samples/drivers/mbox/remote/src/main.c b/samples/drivers/mbox/remote/src/main.c
index f1ae878f3e6..811e03512bf 100644
--- a/samples/drivers/mbox/remote/src/main.c
+++ b/samples/drivers/mbox/remote/src/main.c
@@ -31,13 +31,16 @@ void main(void)
 	mbox_init_channel(&tx_channel, dev, TX_ID);
 	mbox_init_channel(&rx_channel, dev, RX_ID);
 
+	if (mbox_register_callback(&rx_channel, callback, NULL)) {
+		printk("mbox_register_callback() error\n");
+		return;
+	}
+
 	if (mbox_set_enabled(&rx_channel, 1)) {
 		printk("mbox_set_enable() error\n");
 		return;
 	}
 
-	mbox_register_callback(&rx_channel, callback, NULL);
-
 	while (1) {
 
 		printk("Ping (on channel %d)\n", tx_channel.id);
diff --git a/samples/drivers/mbox/src/main.c b/samples/drivers/mbox/src/main.c
index 736771a9b4e..3fa358ef5f2 100644
--- a/samples/drivers/mbox/src/main.c
+++ b/samples/drivers/mbox/src/main.c
@@ -31,13 +31,16 @@ void main(void)
 	mbox_init_channel(&tx_channel, dev, TX_ID);
 	mbox_init_channel(&rx_channel, dev, RX_ID);
 
+	if (mbox_register_callback(&rx_channel, callback, NULL)) {
+		printk("mbox_register_callback() error\n");
+		return;
+	}
+
 	if (mbox_set_enabled(&rx_channel, 1)) {
 		printk("mbox_set_enable() error\n");
 		return;
 	}
 
-	mbox_register_callback(&rx_channel, callback, NULL);
-
 	while (1) {
 		k_sleep(K_MSEC(2000));