He was well known in the science fiction community for his role in the 1983 NBC miniseries V and 1984 sequel V: The Final Battle, as John, the Visitors' Supreme Commander.

Other major roles in his career included recurring parts on the NBC series seaQuest DSV as Admiral William Noyce; on Star Trek: Voyager as Admiral Owen Paris, the father of helmsman Tom Paris; and as George Costanza's boss Matt Wilhelm on Seinfeld.

In two guest appearances on Quantum Leap, he played children's show host "Captain Galaxy", a would-be time traveler, and a miner named Ziggy Ziganovich.

Herd's first major film role was in the thriller The China Syndrome alongside Jane Fonda, Jack Lemmon and Michael Douglas, where he played the character Evan McCormack, the corrupt Chairman of the California Gas & Electric Board.

In 2012, he played Judge Paul Landsman in the TV series CSI: Miami episode "Rest in Pieces".