She began pursuing mixed martial arts (MMA) at an early age and set her eyes on becoming a professional fighter.
[15] Mayce Barber faced Jamie Colleen at Dana White's Contender Series 13 on July 17, 2018.
[17] Barber faced JJ Aldrich at UFC Fight Night: Thompson vs. Pettis on March 23, 2019.
[23] After a year of hiatus recovering from a knee injury, Barber faced Alexa Grasso on February 13, 2021 at UFC 258.
[28] Barber was expected to face Montana De La Rosa on December 11, 2021 at UFC 269.
[29] However, De La Rosa pulled out of the fight in early October citing injury[30] and she was replaced by Erin Blanchfield.
[32] Barber faced Montana De La Rosa on April 23, 2022 at UFC Fight Night 205.
[34] Barber, replacing injured Casey O'Neill, faced Jessica Eye on July 2, 2022, at UFC 276.
[46] However, Barber withdrew from the bout, due to what was later revealed to be ongoing health problems, and was replaced by Tracy Cortez.