De La Garza shared the happy news that her daughter will be born this summer on her official Twitter account on Saturday (February 9).
"Yea!!!! So thrilled to share the news of our new baby girl... Coming in July," the Ohio-born star wrote.
The actress previously welcomed her older son Kieran Thomas Roberts in September 2010.
De La Garza and her husband Roberts, a writer, tied the knot in May 2008 in Orange County, Florida.
She is perhaps best known for playing ADA Connie Rubirosa on Law & Order and the spinoff Law & Order LA.
De La Graza also famously portrayed Marisol Delko-Caine in CSI: Miami and Aethyr on Smallville.