The party, which took place at U2 manager Guy Oseary's house, also marked Bono's daughter's birthday, reported Us magazine.
"You've changed the world with everything you do. You give people hope, especially with your song 'Sunday, Bloody Sunday'," Williams said.
Bono replied, "Well, if we just keep singing 'Happy', we won't need songs like 'Sunday, Bloody Sunday!'"
Other performers included Jon Batiste as well as ASAP Rocky, who personally sang the U2 singer's daughter 'Happy Birthday'.
The following day, Bono joined George Clooney and fiancee Amal Alamuddin to celebrate their recent engagement in Malibu, California, at Cafe Habana.