MacArthur graduated from high school at Deerfield Academy. After that, he enrolled at Bowdoin College to earn a bachelor's degree in government. To pursue his interest in acting, he later also enrolled at the Groundlings Theater Company and Atlantic Theater Company.

He made his feature film debut in Homo Erectus, playing Tudnik. However, he is most widely known for his role as Jay Geils on the series Angie Tribeca. His other acting credits include Go On, Worst Week, House of the Damned 2, Being Frank, and others. He has also appeared as a guest on popular shows such as How I Met Your Mother and Happy Endings.

—via yahoo movies