The star’s name trended on Twitter on Tuesday after clips and pictures of him wearing dark make-up to portray comedian and former SNL star Chris Rock began circulating.
Responding to criticism, Jimmy tweeted: “In 2000, while on SNL, I made a terrible decision to do an impersonation of Chris Rock while in blackface.
“There is no excuse for this.
“I am very sorry for making this unquestionably offensive decision and thank all of you for holding me accountable.”
Jimmy appeared on SNL from 1998 until 2004, leaving the show to pursue film roles, later becoming the sixth permanent host of the late night US chat show The Tonight Show in 2014.
SNL has an established history of casting non-Black actors in Black roles, with Billy Crystal playing Sammy Davis Jr in 1984 and more recently former US president Barack Obama was portrayed by Fred Armisen.
Jimmy’s fellow late night host Jimmy Kimmel has also faced similar criticism for wearing dark make-up to impersonate Oprah Winfrey in a sketch previously.