John Stamos is one protective papa bear.

In fact, the Full House alum revealed he totally lost his cool when his son Billy recently experienced a new milestone.

"He got a haircut recently and I've been in therapy for that," Stamos exclusively told E! News July 16 at the season two premiere of his show Unprisoned in New York City. "I've had some anxiety attacks and it's been traumatic for me." (Watch E! News tonight, July 17, at 11 p.m. for more exclusive scoop from the premiere.)

However, the 60-year-old tried hard to hide his emotions from the 6-year-old.

"I did the best acting in the world when I saw him," he added. "I was like, 'That looks great, son!' But he liked it and I freaked out."

Since welcoming Billy with wife Caitlin McHugh in April 2018, Stamos admitted, "I cry a lot more. I worry a lot more. I'm always worried."

As for what Stamos loves most about watching his only child grow up?

"His sense of wonder," he gushed. "I love to watch him see things for the first time, I love to see his point of view on things. He's my life. I don't know where I would be without having a kid."

And after six years of marriage, Stamos is equally amazed by Caitlin.

"I'm in awe of her, she does so much," he shared. "She really puts her money where her mouth is. She's gotten involved with all these charities."

In fact, Billy has already started taking part in his parents' philanthropic endeavors.

"She also includes our son and that's what I love about her," the actor noted. "He had a pirate party and so we emulated that same party for a bunch of homeless kids down in Orange County. He grabbed a bunch of his toys and he physically handled them to the other kids."

See more of Stamos on E! News tonight, July 17, at 11 p.m. Season two of Unprisoned is streaming now on Hulu.

And keep reading to look back and his cutest family photos with Billy.

John and Billy appear in a video the actor posted on his 60th birthday.

John Stamos and Caitlin McHugh brought their son Billy Stamos to Disney Junior's "Glow Webs Glow" event celebrating the second season of Marvel's Spidey and His Amazing Friends in August 2022.

The duo rocked serious looks during their trip to NYC in December 2022. 

"UFO welcoming committee," Stamos captioned a photo of him and Billy posing with Iron Man in July. 

Billy paid Stamos a visit on the set of his Disney+ series Big Shot.

The father-son pair snuggled at cruising altitude in this pic that was shared in mid-July.

Stamos and McHugh hold Billy and celebrate the Fourth of July.

The actor posts a photo of himself gardening with Billy. 

The People's Choice Awards winner starts off 2019 by posting this precious father-son photo to Instagram.

The Stamos trio donned matching outfits and Santa hats in this adorable pic that's perfect for their 2018 Christmas card.

"Already my favorite Christmas," Stamos captioned a photo of him and his son spending the holiday season at Disney.

While Billy may be too young to vote, the Grandfathered actor encouraged everyone to get out and vote during the 2018 midterms.

In October 2018, the California native took a dip with his son in the pool.

The ER alum is caught leaning over to give his son a kiss on Billy's first Fourth of July.

McHugh snapped this adorable pic of her husband and son on her birthday writing, "I'm the luckiest birthday girl in the world to spend today with you two."

Stamos went from everyone's favorite fictional uncle to real-life dad in April 2018 when his and wife Caitlin McHugh's son Billy was born. The sitcom star introduced little Billy to his Full House co-stars Bob Saget and Lori Laughlin.