Among his early acting work were stints on assorted Canadian TV series such as Cold Squad. He also appeared on the TV show Smallville and he portrayed a police officer for a predominantly gay neighborhood in an episode of The L Word.
In 2003, Tahmoh was cast in a reimagining of the 1978 sci-fi series Battlestar Galactica. He has also lent his voice to Robot Chicken.
Tahmoh voices supporting character Troy Hammerschmiddtt in 2009's Titan Maximum.