The 32-year-old actress gave birth Wednesday to Avery Grace Sehorn in her hometown of Dallas, publicist Troy Nankin said.
This is the second child for Harmon and Sehorn, 34, a one-time cornerback for the New York Giants. They have a 20-month-old daughter, Finley Faith.
Harmon and her family plan to spend the rest of the summer in Dallas before returning to Los Angeles in the fall, Nankin said. No other details were released.
Harmon will next be seen on screen with Jim Carrey and Tea Leoni in December's "Fun with Dick and Jane," a remake of the 1977 comedy.