She rose to prominence portraying Tabitha Ford in the Australian soap opera Home and Away (2016), before receiving critical acclaim for playing a troubled teenager in the HBO miniseries Sharp Objects (2018).

[3] She then achieved recognition for her portrayal of Amma Crellin in the HBO psychological thriller miniseries Sharp Objects, in which she stars alongside Amy Adams.

[5] In 2019, she portrayed Beth March in Greta Gerwig's adaptation of Louisa May Alcott's novel Little Women, co-starring alongside Saoirse Ronan, Emma Watson, Florence Pugh, Laura Dern, Timothée Chalamet, and Meryl Streep.

[7][8] In 2020, Scanlen portrayed Lenora in Antonio Campos' thriller The Devil All the Time, based on Donald Ray Pollock's book.

In the same year she made her directional debut with the Australian short film Mukbang which received much controversy, she also wrote the screen play.