Walker would have turned 48 on Sunday and his Fast & Furious co-star didn't let the birthday pass without acknowledging his friend.
"So much to tell you," Diesel, 54, began his social media post, alongside a photo of them on the set. "Normally I would say you wouldn’t believe how I spent your birthday... but by the safe outcome, I know you were there with me in spirit."
He ended it with, "Miss you. Always."
Commenters replied with crying and heart emojis as well as the word "family," which the Fast & Furious crew became, now nine movies in — spin-offs not included.
Paul died in a November 2013 car crash. He was at an event for his charity, Reach Out Worldwide, when the Porsche Carrera GT he was a passenger in crashed and caught fire. Speed was to blame, as well as other factors. There were multiple lawsuits.
Paul's brothers, Caleb and Cody, were brought in as a stand-in for their brother who was in production for Fast 7 at the time.
Diesel took Paul's only daughter, Meadow Walker, under his wing. Their bond developed long ago, as he was already her godfather. Meadow — now a model, who's been a fixture at New York Fashion Week — attended the F9: The Fast Saga in June with her F&F family, who are all protective of her.
Diesel has said he hasn't ruled out Meadow appearing in Fast 10.
Meadow posted her own tribute to the late star on his birthday. She was a young child in the photo alongside her dad and she wrote, "Happy birthday daddy. I love you."
Diesel replied to Meadow's tribute with prayer hands.
Fast & Furious stars Michelle Rodriguez, Jordana Brewster and Tyrese remembered him as well.