The 61-year-old actor has shown his support for his former Full House co-star during his cancer battle, just days after he revealed he has been diagnosed with stage three non-Hodgkin's lymphoma.
Sharing photos of himself shaving his friend's head on Instagram, he wrote: "Nothing like throwing on a bald cap and flexing some Photoshop skills to show some love and solidarity with my bro @dcoulier.
"You're handling this with so much strength and positivity - it's inspiring. I know you're going to get through this, and I'm proud to stand with you every step of the way. I love you."
And he added a sweet tribute to Coulier's wife Melissa, describing her as his pal's "true life line".
View this post on Instagram A post shared by John Stamos (@johnstamos)
Stamos and Coulier have been close friends since starring on the 1990s sitcom together.
When Coulier shared his diagnosis, Stamos immediately promised to be by his side.
The 65-year-old actor was diagnosed just five weeks before he revealed the news publicly.
He told Today show host Hoda Kotb: "In that time, I've had three surgeries, I've had chemo, I've lost a little bit of hair.
"I kind of look like a little baby bird now, but it has been a roller coaster ride for sure."
Coulier revealed he is battling "a very aggressive type of lymphoma", but he's glad that the cancer hasn't spread.
"At that point, the curability rate went up to 90 plus per cent. So it's very treatable," he said.
And Coulier had told his wife he would be "OK with whatever the news" was.
"I can't explain where that came from. I've had an incredible life. I've had the most amazing people in my life," he said.
"This has been an extraordinary journey, and I'm OK if this is the end of the journey."
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