Vin Diesel sent Paul Walker's daughter a sweet birthday message.

The 'Fast & Furious' actor - whose co-star tragically passed away in 2013 at the age of 40 when he was involved in a car crash - posted a touching tribute on Instagram to mark Meadow's 21st birthday as he said he's ''always been proud'' of her.

He wrote: ''I could say that I am so proud of the person you are becoming... but the truth is I have always been proud of you.

''Happy Birthday Meadow! I know it's your 21st and you wanted to go big in Japan, but the family has a cake waiting for you when you get home, so hurry. Love you kid. Uncle Vin.''

Meadow responded: ''Thank you so much. I can't wait to see you soon. And my little angels. Love you.''

Meanwhile, Vin - who named his four-year-old daughter Pauline in honour of his pal - paid his emotional respects to his late friend in September to mark what would have been Paul's 46th birthday.

He shared a lengthy post in which he spoke directly to the late actor, and caught him up on everything that has been happening in their hit franchise.

He wrote: ''Normally today I would be planning how to embarrass you with a birthday cake. Haha. Instead I reflect on how lucky I am to call you my brother.

''The tears never go away, but they change... from that of mourning to that of grace. We only hope to make you proud.

''Speaking of which, guess what message I woke up to... your daughter. Meadow sending me love on this day. Wow, she knows me so well.

''She has your heart. Happy birthday... it's amazing, but somehow you continue to make the world a better place. (sic)''