Born and raised in Massachusetts, Harrington studied theater at Syracuse University before he began acting professionally on stage and screen.
Harrington resides in Los Angeles and is an avid sports fan who plays in the Entertainment League, a private celebrity basketball league (formerly the NBA-E League), and skates for a local amateur ice hockey team.
Harrington has been featured in lead or ensemble roles in a number of television series in the last few years: as Dr. Simon O'Keefe on the transient WB drama Summerland; as FBI Special Agent Paul Ryan on FOX's short-lived The Inside, opposite Peter Coyote and Rachel Nichols; and as Steve on another short-lived television show, NBC's version of Coupling.
Additionally, Harrington recently appeared in a recurring role on the cable police drama The Division. His other television credits include guest-starring roles on A.U.S.A., The Shield, Time of Your Life, Private Practice and USA Network's Burn Notice.
In 2006, he began appearing as Dr. Ron McCready on the series Desperate Housewives. He also appeared in an episode of Burn Notice as a well-connected brother of a gangster who the series' protagonist goes after to help his battered wife and children.
Harrington starred as Ted Margaret Crisp in the comedy series Better Off Ted, which began on March 18, 2009 and ended on January 26, 2010.
Harrington has appeared in several feature films such as Whatever It Takes and Anywhere but Here, as well as in the independent features Catalina Trust, A Little Inside, and Partner(s). He has also performed on stage, starring as Jack in Boy's Life and appearing in the off-Broadway productions Barefoot in the Park and Tony and Tina's Wedding.