"I always wanted to have one, and I was hoping that it didn't involve pills and a strand of pearls," she joked on stage.
Lady Gaga was one of several musicians who performed at the Hollywood Bowl for "A Decade of Difference: A Concert Celebrating 10 Years of the William J. Clinton Foundation" on Saturday night.
Gaga sported wavy blonde hair and red lips like Marilyn Monroe, who famously crooned "Happy Birthday, Mr. President" to President John F. Kennedy in 1962. The pop star similarly serenaded Clinton, who turned 65 on Aug. 19.
Clinton was seen enjoying the show with his wife Hillary and daughter Chelsea.
"I am the only person in history who got to be President and then had a post-presidential birthday party attended by both Lady Gaga and the Secretary of State," Clinton joked. "I want to thank Hillary because we met 40 years ago this year. When I met her, she was already doing the kind of work you see here long before it was cool."
During her performance, Gaga also swapped the title of "Bad Romance" for "Bill Romance," and told Clinton, "I wish you were playing sax with me tonight, baby."
Other performers included Bono and The Edge, Stevie Wonder, Kenny Chesney, Somali rapper K'Naan, Colombian singer Juanes and Usher.
Ticket prices for the star-studded show ranged from $50 to $550. It also streamed live on Yahoo.com.
The Clinton Foundation seeks to improve global health, strengthen economies worldwide, promote healthier childhoods and protect the environment for the past decade.
The Associated Press contributed to this report.