Amponsah began his acting career with stage roles at the Shaw Festival in the early 2010s.[3] He returned to the stage in the latter half of the 2010s, beginning with a 2016 production of Brandon Crone's play Contempt.[1]
In 2017 he appeared in a production of Salvatore Antonio's Sheets, in a role which called for him to appear on stage in the nude.[4] In the same year he appeared in two third-season episodes of Killjoys as Havigan, the proprietor of a hackmod bar,[5] and starred in Sherren Lee's award-winning short film The Things You Think I'm Thinking.[6]
In 2018, he was profiled in Jamie Miller's short documentary film Prince's Tale,[7] and played a leading role in a production of Judith Thompson's play After the Blackout.[8] In this era he also had guest roles in the television series Frankie Drake Mysteries, The Handmaid's Tale and Private Eyes.
In 2021 he appeared as August, a member of the Traveling Symphony, in the television miniseries Station Eleven,[9] and performed in "Emmett", Syrus Marcus Ware's contribution to the 21 Black Futures project.[10]
In 2022 he had a recurring role as Marvin in the web series Avocado Toast,[11] for which he received a Canadian Screen Award nomination for Best Supporting Performance in a Web Series at the 11th Canadian Screen Awards in 2023.[12] His role in the series was hailed as a positive step forward for representation of people with disabilities, as his disability was narratively acknowledged but not dwelled upon as the defining aspect of his character's story.[11]
In July 2025, it was announced that Amponsah will play the lead in How Dare You, a forthcoming horror comedy by the filmmaking duo of Kit Redstone and Arran Shearing.[13] Also in 2025, Amponsah appears as Henry Sickler in the Apple TV series The Last Frontier.