In 2005, MacArthur co-wrote, produced and starred in a 16-minute short film, The Adventures of Big Handsome Guy and His Little Friend, with Jason Winer.
He acted as the male lead for three seasons opposite Rashida Jones in Angie Tribeca on TBS, created by Steve Carell.
[5][6] He was a series regular alongside Dennis Quaid in television show Merry Happy Whatever for Netflix.
MacArthur became engaged to Heroes actress Ali Larter, his girlfriend of three years, in December 2007.
[16] On August 1, 2009, MacArthur married Larter in a small ceremony[17][18] at his parents' estate in Kennebunk, Maine.
MacArthur volunteers and serves on the board of directors of Higher Ground USA, a charity that provides recreational therapy for military veterans, first responders, and people with disabilities.
The award is given to an artist that has shown consistency in volunteering for The Art of Elysium, a Los Angeles based charity that provides acting, art, comedy, music, and creative writing workshops for ill children confined to long term stays in hospitals.