[3] Mallard made his acting debut in 2014 at the age of 15, taking over the role of Ben Kirk in the Australian television soap opera Neighbours for a three-week, six episode guest stint.

[14] After finishing Year 12, Mallard chose to pursue acting full-time and he re-joined Neighbours as a permanent cast member in 2016.

[2][16] That same year, he starred in Xanthe ♥ Ben, a 20-episode online spin-off released on Instagram,[17] as well as the webisode series Summer Stories, broadcast during the 2016 Christmas period.

His final storyline as Ben saw him move to his late father's home town of Oakey, Queensland to start over.

[23] Following his departure from Neighbours, Mallard starred in his former co-star Travis Burns's short film Money Is Just a Barbell, which he also produced and did the music.

[24] He moved to the United States at the start of 2018 and quickly secured the role of popstar Cooper James in the CBS comedy series Happy Together, alongside Damon Wayans Jr. and Amber Stevens West.

Happy Together is loosely based on the experiences of English singer Harry Styles, who moved in with television producer Ben Winston and his family to escape the spotlight when the pop band One Direction exploded in popularity.

[9][34][35] Mallard plays series regular Marcus, an edgy 15-year-old, in the Netflix dramedy Ginny & Georgia.

[36] Mallard was required to learn American Sign Language for the role, as his character's father is deaf.