The couple welcomed a daughter, named Arlo Day Brody, on August 4. According to the birth certificate obtained by TMZ, Arlo was born at 12:12am in Whittier, California.
The couple are yet to confirm the arrival of their child. They also did not confirm their nuptials after they secretly tied the knot in February 2014.
Neither did the couple officially confirm they were expecting a baby. However, paparazzi pictures documented 29-year-old Meester's growing baby bump throughout the summer months.
Meester and Brody, best known for his role as Seth Cohen in "The OC", met in 2011 on the set of "The Oranges" in which they co-starred.
They began dating the following year and became engaged in November 2013.
Meester rose to prominence in 2007 when she starred as Blair Waldorf in "Gossip Girl". Her on-screen and off-screen friendship with her co-star Blake Lively made her especially popular with fans of the show.