Publicist Lewis Kay says the couple is separating after nine years of marriage. The breakup was first reported by Us Weekly.
Poehler and Arnett have two sons, Archie, 3, and Abel, 2.
Poehler, 40, became famous as a cast member on "Saturday Night Live." She now stars in the NBC sitcom "Parks and Recreation" and is up for an Emmy for lead actress in a comedy series. Arnett's breakout role was on Fox's "Arrested Development."