Maggie Siff was born on June 21, 1974, in The Bronx, New York City, to a Russian Jewish father and an Irish-Swedish Protestant mother. She attended The Bronx High School of Science and later graduated from Bryn Mawr College with a degree in English. Siff went on to earn an MFA in acting from New York University's Tisch School of the Arts.

She began her career in theater, winning a Barrymore Award for Excellence in Theater in 1998 for her performance in Henrik Ibsen's "Ghosts".

Maggie Siff transitioned to television and film in the mid-2000s, gaining recognition for her role as Rachel Menken Katz on the AMC drama "Mad Men" from 2007 to 2008. She also starred as Dr. Tara Knowles on the FX drama "Sons of Anarchy," for which she received two Critics' Choice Television Award nominations for Best Supporting Actress in a Drama Series.

Her other notable roles include psychiatrist Wendy Rhoades on the Showtime series "Billions" and appearances in films such as "Push" (2009) and "Leaves of Grass" (2010).