[1] Sergent's acting career began at age 15 playing Lionel in the soap opera, Close to Home.
[2] In television Sergent is known for playing Eric Grady on Outrageous Fortune, the New Zealand Prime Minister on Flight of the Conchords, and Harold in The Lost Children.
One of his most popular characters, cabin steward Gavin Soper, appeared on the Pulp Comedy television series.
[3][4] Sergent's film credits include Peter Jackson's Meet the Feebles, Braindead and Lord of the Rings, Absent Without Leave, Via Satellite, the lead role as Marty in The Shirt and Jonah in Eagle vs. Shark.
In 1994, he won Best Male Actor in a Supporting Role for his performance of Gary Peter Lefkowitz in I Hate Hamlet at the Circa.