A spokesman for the couple said they welcomed son Abel James Arnett Friday morning. Publicist Lewis Kay said Abel weighed 7 pounds, 13 ounces and the whole family is "healthy and resting comfortably."
The two actors are also parents of son Archie, born in October 2008.
Poehler is up for an Emmy for her leading role on the NBC comedy "Parks and Recreation." Her other credits include "Saturday Night Live" and the movie "Baby Mama."
Arnett is also nominated for an Emmy this year for a guest appearance on "30 Rock." His other credits include "Arrested Development" and the recent films "Jonah Hex" and "Despicable Me."