Diller, the former Disney chief, takes a seat on the board alongside Barry Diller, who stepped down as IAC’s CEO in December, but retained his board seat.
With the addition of Eisner, IAC’s board is now comprised of 13 members: Eisner, Diller, Greg Blatt, Edgar Bronfman, Jr., Victor Kaufman, Don Keough, Bryan Lourd, Arthur Martinez, David Rosenblatt, Alan Spoon, Alexander von Furstenberg, Richard Zannino and Michael Zeisser.
IAC owns dozens of websites, including Ask.com, College Humor the Daily Beast, which recently finalized a deal to run Newsweek.
Eisner also serves on the boards of the California Institute of the Arts, Denison University, the Aspen Institute, the Yale School of Architecture Dean's Council and his own Eisner Foundation.
Eisner, a former president of Paramount, founded the media and entertainment investment firm Tornante in 2005. He also serves as the chairman of Vuguru, the digital TV studio.