Bryce James had his Senior Night on Thursday, and with the Lakers on an off day -- both LeBron and Bronny made it out to celebrate!

The two L.A. stars -- wearing matching sweatshirts -- drove to Sierra Canyon H.S. to watch Bryce's final home game ... and they were joined by Savannah and little Zhuri too.

They all had some sweet seats for the affair -- sitting right on the court -- and they even got to take some pics with Bryce before his tilt to commemorate the special night.

The 6-foot-4, four-star prospect then went on to put on a show in front of his family -- ending the evening with 12 points, five rebounds and four assists in an 84-42 win.

King James was very emotional about the game afterward, writing on Instagram, "Can't believe he's a SENIOR!!" -- while adding several emojis.

Diddy's kids, Jessie, D'Lila and Quincy were also in attendance. Popular radio host Big Boy showed up as well.

Bryce will now be off to Arizona soon -- he just committed to play for the Wildcats two weeks ago -- but the James Gang will likely have one last Senior Night to attend at some point in the future ... as Zhuri's showing some big-time volleyball promise.