The former Brat Pack member has joined the cast of the "Gossip Girl" spinoff, about the wild young life of Lily Rhodes in the 1980s, according to The Hollywood Reporter.
McCarthy will play Rick Rhodes, the music company exec father of Lily, who will be portrayed by Brittany Snow. Krysten Ritter will play her older sister Carol.
On the original show, the older Lily is played by Kelly Rutherford.
McCarthy was last seen on NBC's "Lipstick Jungle."
In other CW casting news, Tim Matheson has joined the pilot for the Washington, D.C.-set "Body Politic" as a charismatic, JFK-type senator.