She played Annie Whitman on ABC's Life As We Know It. Darr's previous television appearances include The WB's teenage drama, Popular, as Jane McPherson as well as the short-lived but critically-acclaimed 1996 Fox series Profit as Gail Koner. In the fifth season of the show Ellen, she played Laurie Manning, the girlfriend of the title character, Ellen Morgan; this was notable as the first openly gay relationship involving a major character in an American television series.
Darr also made an appearance on the Fox] drama House in 2006, playing a victim's mother in the episode "Distractions". Darr has recently appeared in the fourth season of Weeds (on Showtime) as Ann Carilli.
Her film work includes the Oscar-award-winning Gods and Monsters (1998), in which she appeared as Dana Boone, Brendan Fraser's wife, Pomegranate (2005) and Julia, Leah Pipes's mother, in the soccer film, Her Best Move (2006).