Dwayne 'The Rock' Johnson brings stunt double to tears with custom-built truck

Dwayne 'The Rock' Johnson might be known for his bulging muscles, but he's proved his heart is just as big.

The 46-year-old actor posted a video to his Instagram on Monday (local time) showing him surprising Tanoai Reed, his long-time stunt double and cousin, with a custom-built truck.

The two men were in a car park under the premise of filming a question and answer video, before Johnson began talking about their 17-year working relationship.

He said Reed, who was still recovering from a stunt-related injury, had been "an incredible partner and brother to me".

The Instagram caption to the video revealed that the stuntman had broken multiple bones, severed tendons and torn ligaments during his career.

"I wanted to say thank you, I love you and enjoy your new truck," Johnson said, before turning around to reveal the tricked-out vehicle complete with a big pink bow.

Reed was lost for words, clasping Johnson in an emotional embrace before going to check out his new vehicle.

"Love you uso and thank you for the blood, sweat, tears and years," Johnson ended the Instagram post.