He graduated from William Penn Charter School in 1971 and originally entered Yale University as a pre-medical student, but opted to act, instead.

While he was at Yale University, he was a member of the Society of Orpheus and Bacchus, the second-longest running undergraduate a cappella group in the United States.

Also, while at Yale, he had a major role in the 1973 European premiere production of Leonard Bernstein's Mass in Vienna, conducted by John Mauceri.

His first breaks were appearing in the David Mamet play Sexual Perversity in Chicago, and with Diane Keaton in The Primary English Class.

He made his feature-film debut as Eddie Quist, the serial killer werewolf in the Joe Dante film The Howling (1981).

In 1993, Picardo had a brief role as Joe "the Meat Man" Morton, a butcher and neighbor to Tim Allen's character on the sitcom Home Improvement.

On February 5, 2008, Picardo was announced to be joining the regular cast of Stargate Atlantis full-time for the series' fifth and final season.

In 2007, he played Principal White in Ben 10: Race Against Time, and starred in the independent feature film by director Russ Emanuel, P.J., alongside John Heard and Vincent Pastore.

Picardo appeared on four episodes of E-Ring, as an enraged father in Cold Case, and as a police officer in CSI: NY.

[11] Picardo's other career highlights include performing in Leonard Bernstein's Mass during its European debut tour, performing with the Yale University Society of Orpheus & Bacchus a cappella singing group as an undergraduate, and dozens of other television and film roles, including the film Our Last Days as Children.

In 2009, he appeared in Pushing Daisies, Chuck, and Castle, and had the lead role in the independent psychological thriller film Sensored.

In May 2014, Cartoon Hangover announced Picardo as a guest voice actor in the second season of Bravest Warriors, in the episode "The Parasox Pub".