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, 3-year-old Archie and 2-year-old Abel.
Their personal lives may be in turmoil, but professionally, both are on an upswing.
The 40-year-old Poehler 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." The 42-year-old Arnett now co-stars with Christina Applegate on the NBC comedy "Up All Night."