She began her career as a child actress, starring as Agent Olympia in the PBS Kids/TVOKids series Odd Squad (2016–2019) for which she won a Canadian Screen Award.
[12] At the age of 12, following a hiatus,[4] Cathcart was scouted and asked to audition for the TVOKids and PBS Kids series, Odd Squad.
[13] That same year, Cathcart reprised her role for the film spin-off Odd Squad: The Movie, marking her first theatrical appearance.
[citation needed] In November 2016, PBS ordered 20 one to three minute episodes of an Odd Squad spin-off titled OddTube.
[17][18] Cathcart joined the cast of the film adaption of Jenny Han's bestselling book To All the Boys I've Loved Before, in which she was to portray 11-year-old Kitty Song-Covey, the younger sister of protagonist Lara Jean.
"[37] She was nominated for the Cogeco Fund Audience Choice Award..[38] In mid-2020, because of the restrictions placed due to the COVID-19 pandemic, Cathcart hosted a virtual series called Letters To which allowed fans to connect with their favourite authors.
[39][40][41][42][43][44] Developed by Picturestart and released on Facebook Watch, Glitter Magazine wrote that the series had "all literary fans buzzing".
[49] Cathcart's performance was commended by Amy Amatangelo of Paste, who called her the "generation's secret weapon" and stated that projects including her were certain to be of high quality.
[53][54] TheWrap described her as "appropriately sweet",[55] while Comic Book Resources stated she "makes a confident jump to a leading role".