Braving winds that started up earlier in the day, the glammed up stars including David Cook, Adam Lambert and Katy Perry, packed the red carpet, all eager to see the movie made up of rehearsal footage from the tour that never was.
Jennifer Love Hewitt and Jamie Kennedy posed for pictures with Michael Jackson shirts on, as did former "High School Musical" star Ashley Tisdale.
In fact, a host of "HSM" alumni attended the event held at the Nokia Theatre in Downtown LA, including Corbin Bleu and Monique Coleman, who Tweeted at the event, "my heart feels so broke and so filled at the same time."
It appeared to be a family affair for many of the stars at the event too.
Martin Lawrence, who told Access Hollywood he would support anything to do with Michael, brought his two daughters while "Transformers" star Tyrese also brought his little one decked out in sparkling pants.
"at the premier for 'This is it' I brought my 2 year old daughter.." Tyrese wrote on his Twitter page. "She's dancing in my lap.. I just teared up.. MJ still brings joy."
Access Hollywood reported early on Tuesday that the Jackson brothers would attend and they were full of pride as they headed into the premiere.
Jermaine told Access Tuesday's event meant simply, "everything."
As for Paula, she Tweeted following the event.
'I'm sitting in the nokia theater in awe of the 'this is it' movie! So many emotions are coming up For me I can't believe He's gone,." she wrote. "Brilliant."
David Cook also Tweeted that the movie was "MJ doing what he did best…. Incredible."
And across the pond, the London premiere of "This Is It" also brought out the stars. Former Spice Girl Mel B and Harry Connick Jr. were among the many notables who ventured out in Britain to see Michael's curtain call.
For more of the star-studded action from the "This Is It" LA premiere, tune into Access Hollywood on Wednesday night.
Related Content from AccessHollywood.com:
PLAY IT NOW: Preparing For Michael Jackson's 'This Is It'
PLAY IT NOW: Meet The Team Behind Michael Jackson's 'This Is It' Magic