The pair were first linked romantically in August 2010, shortly after Armisen split from his wife, Mad Men star Elisabeth Moss.
However, the comedy couple have now gone their separate ways, with the break-up being described as "completely mutual," according to Us Weekly.
"It definitely wasn't a dramatic break-up," an insider said. "They had different schedules over the summer and are still good friends."
Though sources claimed the relationship was nothing serious, the two dated for around a year before splitting.
Armisen and Moss finalised their divorce in May. The couple were initially reported to have split over Moss's commitment to Scientology, but those claims have since been denied.