The 36-year-old actress' rep confirmed Baccarin and the 37-year-old actor welcomed a baby girl in early March in a statement to news outlets Friday.
"Morena and Ben are so happy to welcome baby girl Frances Laiz Setta on March 2," the rep said. "All are happy and healthy and appreciate the well-wishes."
TMZ reported the couple chose Frances' name to honor their respective mothers. Frances is McKenzie's mom's first name, while Setta is Baccarin's mom's maiden name. Baby Frances will take McKenzie's legal last name, Schenkkan.
Baccarin and McKenzie co-star as Dr. Leslie Thompkins and Det. James Gordon on Fox series Gotham and have been linked since 2015. The couple announced they were expecting in September after attending the Primetime Emmy Awards together.
"[I'm] so excited! I'm ready," the actress told Us Weekly at a New York screening of Deadpool in February. "My water could break right now," she added to E! News. "I want to sleep all day and not be in a dress and heels."
Baccarin is already mom to 2-year-old son Julian with her estranged husband, Austin Chick. The Gotham star delayed a deposition in her divorce last month due to her "high-risk pregnancy," claiming "such stress will affect [her] personal well-being."
Gotham premiered in 2014 and airs Mondays at 8 p.m. ET. The series follows a young Det. Gordon and co-stars Donal Logue as Harvey Bullock, Robin Lord Taylor as Oswald Cobblepot, aka the Penguin, and David Mazouz as Bruce Wayne.