With his famous father sitting courtside and catching the action on his cellphone, Bronny James came off the bench in the first half of the University of Southern California's game against Long Beach State.

James was given medical approval to return to basketball activities in November and returned to training with his USC teammates shortly thereafter.

James, a prized high school prospect closely scrutinised because of his father, opted to play for USC in May.

But in a July workout he collapsed and was hospitalised for three days. His family revealed in August that he had been diagnosed with and treated for a congenital heart defect.

The Galen Center in downtown Los Angeles was packed, LeBron James making his entrance to courtside seats accompanied by daughter Zhuri and son Bryce, who plays basketball for Sierra Canyon high school.

Bronny James got a standing ovation when he entered the game with 12:58 remaining in the first half. He missed his only shot in the first half but drew a roar with a chase-down block that evoked the moves of his famous father.

He scored his first points with a second-half three-pointer that again had fans, including his dad, on their feet.

On Thursday, James said his son's return to the court meant "everything and more.

"I can't wait to see him run out with his teammates," James said. "And then once he checks into the game, whenever that case may be, it's going to be a big moment for our family.

"It's a big milestone for our family, for sure, and it's another step for him on his journey in his basketball career."

Dwyane Wade, who teamed with LeBron James to win two NBA titles in Miami, noted the moment on the X social media platform.

"Watching Bronny walk out on that court gave me chills…" Wade posted. "Welcome back to the game you love Bronny"

Kevin Durant of the Phoenix Suns also offered a shout-out posting "Welcome back Bronny".