Hewlett first gained fame for his roles as Grant Jansky in the Canadian TV series "Traders" (1996—2000) and as David Worth in the Canadian psychological horror film "Cube" (1997). He had earlier appeared in the horror film "Pin" (1988) and the science-fiction film "" (1991). More recently, Hewlett had a prominent supporting role in "Rise of the Planet of the Apes" (2011), portraying bad-tempered airplane pilot Douglas Hunsiker opposite John Lithgow and Andy Serkis. Hewlett played the character Fleming in the multi-Academy Award winning film The Shape of Water (2017).