His most memorable role was Elvis Gratton in which his character impersonates rock and roll icon Elvis Presley. The series of Elvis Gratton films appeared between 1981 and 2004. The most recent of these movies were Elvis Gratton II: Miracle a Memphis, filmed in 1999, in which Elvis was resuscitated from the first film of the series, and ''Elvis Gratton 3: Le retour d'Elvis Wong," which was filmed in 2004.
He also co-directed some of the movies along with Pierre Falardeau.
In addition to the Elvis Gratton movies, Poulin also played several main and supporting roles in other movies and TV series including Lance et compte in 1986, Virginie in 1996, Jasmine and Omerta 2, la loi du silence in 1997, Les orphelins de Duplessis in 1999, 15 février 1839 and Fortier in 2001, Séraphin : un homme et son péché in 2002 and Le Negociateur 1 and Le Negociateur 2 in 2005-2006.
Julien Poulin portrays Gaétan Langlois is the award-winning show Minuit, le soir.
Poulin was the spokesperson for Opération Nez rouge in 1996, a campaign against drinking and driving during the holidays.