diff --git a/targets/TARGET_NORDIC/TARGET_NRF5x/trng_api.c b/targets/TARGET_NORDIC/TARGET_NRF5x/trng_api.c
index 829dac51847..aa00d60749b 100644
--- a/targets/TARGET_NORDIC/TARGET_NRF5x/trng_api.c
+++ b/targets/TARGET_NORDIC/TARGET_NRF5x/trng_api.c
@@ -37,21 +37,45 @@
  */
 
 #if defined(DEVICE_TRNG)
-#include "trng_api.h"
+
+#include "hal/trng_api.h"
+#include "hal/critical_section_api.h"
+
 #include "nrf_drv_rng.h"
 
+/* Keep track of instantiated FlashIAP objects. */
+static int nordic_trng_counter = 0;
+
 void trng_init(trng_t *obj)
 {
     (void) obj;
 
-    (void)nrf_drv_rng_init(NULL);
+    /* Increment global counter inside critical section. */
+    hal_critical_section_enter();
+    nordic_trng_counter++;
+    int counter = nordic_trng_counter;
+    hal_critical_section_exit();
+
+    /* Initialize TRNG on first object only. */
+    if (counter == 1) {
+        nrf_drv_rng_init(NULL);
+    }
 }
 
 void trng_free(trng_t *obj)
 {
     (void) obj;
 
-    nrf_drv_rng_uninit();
+    /* Decrement global counter inside critical section. */
+    hal_critical_section_enter();
+    nordic_trng_counter--;
+    int counter = nordic_trng_counter;
+    hal_critical_section_exit();
+
+    /* Deinitialize TRNG when all objects have been freed. */
+    if (counter == 0) {
+        nrf_drv_rng_uninit();
+    }
 }
 
 /* Get random data from NRF5x TRNG peripheral.
@@ -61,30 +85,35 @@ void trng_free(trng_t *obj)
  */
 int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_length)
 {
-    uint8_t bytes_available;
-
     (void) obj;
 
+    /* Query how many bytes are available. */
+    uint8_t bytes_available;
     nrf_drv_rng_bytes_available(&bytes_available);
 
+    /* If no bytes are cached, block until at least 1 byte is available. */
     if (bytes_available == 0) {
         nrf_drv_rng_block_rand(output, 1);
         *output_length = 1;
     } else {
 
+        /* Get up to the requested number of bytes. */
         if (bytes_available > length) {
             bytes_available = length;
         }
 
-        if (nrf_drv_rng_rand(output, bytes_available) != NRF_SUCCESS) {
-            *output_length = 0;
-            return -1;
-        } else {
+        ret_code_t result = nrf_drv_rng_rand(output, bytes_available);
+
+        /* Set output length with available bytes. */
+        if (result == NRF_SUCCESS) {
             *output_length = bytes_available;
+        } else {
+            *output_length = 0;
         }
     }
 
-    return 0;
+    /* Set return value based on how many bytes was read. */
+    return (*output_length == 0) ? -1 : 0;
 }
 
 #endif
diff --git a/targets/targets.json b/targets/targets.json
index c365f51257a..a1630b0b8ab 100644
--- a/targets/targets.json
+++ b/targets/targets.json
@@ -3442,6 +3442,7 @@
         "device_has": [
             "ITM",
             "FLASH",
+            "TRNG",
             "STCLK_OFF_DURING_SLEEP"
         ],
         "extra_labels": [
@@ -3475,7 +3476,7 @@
         "supported_form_factors": ["ARDUINO"],
         "inherits": ["MCU_NRF52832"],
         "macros_add": ["BOARD_PCA10040", "NRF52_PAN_12", "NRF52_PAN_15", "NRF52_PAN_58", "NRF52_PAN_55", "NRF52_PAN_54", "NRF52_PAN_31", "NRF52_PAN_30", "NRF52_PAN_51", "NRF52_PAN_36", "NRF52_PAN_53", "S132", "CONFIG_GPIO_AS_PINRESET", "BLE_STACK_SUPPORT_REQD", "SWI_DISABLE0", "NRF52_PAN_20", "NRF52_PAN_64", "NRF52_PAN_62", "NRF52_PAN_63"],
-        "device_has_add": ["ANALOGIN", "I2C", "I2C_ASYNCH", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPI_ASYNCH", "SPISLAVE", "TRNG"],
+        "device_has_add": ["ANALOGIN", "I2C", "I2C_ASYNCH", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPI_ASYNCH", "SPISLAVE"],
         "release_versions": ["5"],
         "device_name": "nRF52832_xxAA"
     },
@@ -3549,6 +3550,7 @@
         "device_has": [
             "ITM",
             "FLASH",
+            "TRNG",
             "STCLK_OFF_DURING_SLEEP"
         ],
         "extra_labels": [
@@ -3582,7 +3584,7 @@
         "supported_form_factors": ["ARDUINO"],
         "inherits": ["MCU_NRF52840"],
         "macros_add": ["BOARD_PCA10056", "CONFIG_GPIO_AS_PINRESET", "SWI_DISABLE0", "NRF52_ERRATA_20"],
-        "device_has_add": ["ANALOGIN", "I2C", "I2C_ASYNCH", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE", "TRNG"],
+        "device_has_add": ["ANALOGIN", "I2C", "I2C_ASYNCH", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE"],
         "release_versions": ["5"],
         "device_name": "nRF52840_xxAA",
         "bootloader_supported": true