While an infant, her parents were sent to prison and she was adopted and raised as an only child by her uncle Sam Sweetin and his second wife Janice when she was nine months old.

[7] Sweetin was cast in a guest role in the sitcom Valerie as Pamela, the niece of Mrs. Poole (Edie McClurg).

Jeff Franklin cast her as Stephanie Tanner in the ABC comedy series Full House, and she played that role until the show ended in 1995.

[4] Sweetin returned to television by hosting the second season of the Fuse dance competition show Pants-Off Dance-Off.

In 2015, it was announced Sweetin would reprise her role as Stephanie Tanner on the Netflix spin-off series Fuller House, which ended after five seasons in 2020.

[12] In 2022, Sweetin competed on CBS's Beyond the Edge,[13] the seventh celebrity edition of Food Network's Worst Cooks in America: That's So'90s,[14] and the second season of FOX's Name That Tune.

Over parts of the next 13 years, she abused ecstasy, methamphetamine, and crack cocaine, among others,[35] stating that she turned to drugs because she was "bored".

[36] In 2009, Sweetin wrote the memoir unSweetined, chronicling her downward spiral of alcohol and drug abuse that began with the ending of Full House.

[37] In one passage of the book, Sweetin discusses breaking into tears while addressing a crowd at Wisconsin's Marquette University while coming down from a two-day methamphetamine, cocaine, and ecstasy binge.

[41][42] Sweetin has expressed support for the Black Lives Matter movement, and she was also active with Refuse Fascism,[43][44] to demand the removal of the Trump administration through nonviolent street protests.

On June 25, 2022, Sweetin was shoved by members of the Los Angeles Police Department and fell to the ground while she was protesting for abortion rights in the wake of Dobbs v. Jackson Women's Health Organization, a U.S. Supreme Court decision that overruled Roe v. Wade and Planned Parenthood v. Casey leading to abortion bans in multiple states.