 He had recurring roles on the NBC sitcoms "Up All Night", as Maya Rudolph's on and off lover, Julian; "The Office", as Brian, a former member of the show's documentary film crew (alongside future "Silicon Valley" cast member Zach Woods), and on "Arrested Development", as Marky, Lindsay's face-blind environmentalist boyfriend.He has featured in the UK/US television sitcom "Episodes" playing the part of TV network boss Castor Sotto, Mr. Chris in the TV adaptation of "About a Boy".In 2017 Diamantopoulos starred in the musical "Waitress" on Broadway.