The 28-year-old 'Firework' singer looked sleek in the sequinned floor-length gown at the charity event, which provides support and suicide prevention services to lesbian, gay, bisexual, transgender youths, before being handed the Trevor Hero Award.
Trevor Project CEO Abbe Land said of Perry's award: "We're honouring her because, really, she has done so much to empower youth.
"A couple of years ago when, unfortunately, a lot of young suicides made the news - and there was a very visible presence of suicide - Katy stepped up and was out there in the community, speaking against it.
"Her support of marriage equality - and equality for everyone, really - is one of the many reasons we're supporting her as our hero this year."
Other stars at the bash included Glee's Matthew Morrison and Chris Colfer, Modern Family's Sarah Hyland, Anna Kendrick, Ricki Lake, Vampire Diaries star Paul Wesley, Amy Poehler and Zoe Saldana.