[3][4] She is best known for playing Bridgette Bird on the Showtime series SMILF, based on the 2015 short film of the same title, which she wrote, directed and starred in.

[9][15] In 2009, Shaw first received recognition in the completely improvised Katie Aselton-directed film The Freebie and then as the oddball drunken cheerleader Mary Jo Cacciatore in the 2010 sitcom Blue Mountain State.

Also in 2014, Shaw appeared in another independent feature, the drama Lullaby, which starred Garrett Hedlund and Amy Adams.

[19] In 2016, Shaw reprised her role of Mary Jo Cacciatore from the 2010 series in the movie Blue Mountain State: The Rise of Thadland.

[20][21] In 2015, SMILF was picked up by Showtime as a half-hour comedy television show with Shaw as showrunner, writing, directing, starring in, and producing the series.

[22] The first season, which was shot on location in South Boston as well as Los Angeles, received generally positive reviews,[23][24] with her portrayal of single mother Bridgette Bird notable for its realism, insight, and biting humor.

"[27] SMILF co-stars Connie Britton and Rosie O'Donnell,[28][9][29] and tackles subjects like eating disorders and sexual abuse.

"[36] In 2017, Shaw had a supporting role as Gail Hurley in the feature film Stronger, which was directed by David Gordon Green, and starred Jake Gyllenhaal as 2013 Boston Marathon bombing survivor Jeff Bauman.

[3][37] In 2019, it was reported that Shaw is attached to direct an adaption of the Katherine Faw Morris novel Ultraluminous, produced by Steven Soderbergh.