Leighton started her acting career at the age of 10 in her home town, and got her first agent at the age of 12 when she started taking acting classes and going to auditions in Los Angeles. She also has 11 years of dance experience, which she used in ABC Family's Make It or Break It, where she played a gymnast named Wendy Capshaw.[7] In June 2015, Leighton was cast to voice Blossom in Cartoon Network's revival of The Powerpuff Girls, which ran from 2016 to 2019.[8]
Leighton's other appearances include roles on several television shows including Pretty Little Liars as Danielle, Grey's Anatomy as patient Sarah Cassidy with Treacher Collins syndrome, 90210 as Alex Scarborough, Criminal Minds as Trish Leake, and as a singing Cactus Kid in Six Feet Under. She recurred as Emma on the ABC Family/Freeform drama series The Fosters from 2014 to 2018.[9] From 2017 to 2022, she recurred as young Sophie on the NBC television drama series This Is Us.[9][10] Leighton voiced the regular roles of Poppy in the animated series Trolls: The Beat Goes On! which was released by Netflix between 2018 and 2019,[11] and the pollywog Polly Plantar in the Disney Channel animated series Amphibia, which aired from 2019 to 2022.[12] She costarred in the 2020 drama film Chance.[13]
