She gained recognition for playing Betty Cooper on the CW teen drama series Riverdale (2017–2023).

[3][4] She developed a love for singing, acting, and dancing at the age of 10, and asked her mom to drive her to New York City for auditions.

[6] She also starred in the films Lilith (2011), Not Waving But Drowning (2012), The Kings of Summer (2013), Gibsonburg (2013), Forever's End (2013), Miss Stevens (2016), and The Good Neighbor (2016).

[7][8] On February 9, 2016, Reinhart was cast as Betty Cooper in The CW's teen drama television series Riverdale, based on the characters of Archie Comics.

[9] Series creator Roberto Aguirre-Sacasa originally sought out Kiernan Shipka for the role after seeing her work in Mad Men.

[19] Reinhart played Annabelle, "the baby of the group," a former stripper who joins Ramona and her crew in drugging and robbing their Wall Street clientele.

[22] Hustlers premiered at the Toronto International Film Festival on September 7, 2019,[23] and was theatrically released in the United States the next week.

[26] The same year, Reinhart made a cameo appearance during the mid-credits scene of Elizabeth Banks' Charlie's Angels (2019).

In May 2020, Reinhart voiced Bella-Ella, "a ... snooty rich [girl]" in the Simpsons episode "The Hateful Eight-Year-Olds".