The event, which will also feature a performance by "So What" singer Pink, takes place Wednesday at Beverly Hills' SLS Hotel.
Criss revealed his participation via his Twitter account Tuesday, writing, "So bummed I'll have to miss my dental appointment to sing for The US President Wed night. thanx @Pink for messin that up!!"
For the irony-impaired, Criss added, "But in all seriousness @Pink- what an honor!"
In addition to his acting duties, Criss has launched a musical career, releasing an independent EP, "Human," in 2010. Criss is signed with Sony Music Entertainment, with an eye toward releasing a full-length studio album.
Obama became the first U.S. president to come out in favor of marriage equality in May, telling ABC News' Robin Roberts, "I’ve just concluded that for me personally it is important for me to go ahead and affirm that I think same sex couples should be able to get married."
