In 1995, Rennie's feature career took off, with a memorable supporting turn in Mina Shum's "Double Happiness", acting opposite Sandra Oh as the boyfriend that her Chinese immigrant parents disapprove of because he is Caucasian. The actor's work in this celebrated Canadian independent won him notice and acclaim, and his portrayal of the awkward bespectacled suitor was most engaging. That same year, Rennie starred as recovering heroin addict Jim in the experimental film adaptation of Jim Carroll's autobiographical short story "Curtis' Charm" (released in the USA in 1996). This project, vastly different than "Double Happiness", featured the actor's unflinching and compelling performance, and proved him a performer of varied abilities. Later in 1995, he could be seen on the small screen in the USA Network thriller "When the Dark Man Calls" and the ABC adventure "The Ranger, the Cook and a Hole in the Sky". A small role as a drug dealer followed in the 1996 feature thriller "Unforgettable", and that same year Rennie would give an impressive starring performance in Canadian filmmaker Bruce McDonald's "Hard Core Logo" (released in the USA in 1998), a satirical but heartfelt punk rock mockumentary. He played Billy Tallent, a big talking member of the titular band, a defunct legend of the Vancouver punk scene. Small roles in the children's adventure film "Masterminds" and the romantic comedy "Excess Baggage" followed in 1997, as well as a turn as a bumbling stoner in the independent adventure film "Men With Guns".
Rennie's prolific work won him the notice and acclaim of the Canadian press which named him an up-and-comer to watch. This new high profile led to extensive work in television in 1997, as a featured cast member in the Canadian TV series "My Life as a Dog" (aired in the USA on Showtime). Here he played Uncle Johnny Johansson, earning a 1997 Gemini Award for his work. Also on Showtime, Rennie co-starred in original movie "Tricks", chronicling the life of a single mother who turns to prostitution in order to earn enough money both to care for her ailing son and to put herself through college. From 1997 to 1999, Rennie had a regular role on the series "Due South", replacing previous regular David Marciano for the syndicated fourth season (aired in the USA on TNT), in which he utilized a grating Chicago accent to play Detective Stanley Kowalski, the new American partner of transplanted Mountie Benton Fraser on the Canadian produced police series. Intriguing as the hardened streetwise Chicago detective opposite Paul Gross' always polite Canadian Mountie, Rennie brought a smoldering and sarcastic edge to the quirky police series. A hugely successful show in Canada, "Due South" offered Rennie visibility, but at the same time caused some problems in his career, plagued by the cries of "sell out" that so often come with commercial success after a run of hard work in independents.
Despite these disparaging artistic accusations, the actor returned to film in 1998, slipping easily back into the supportive and insulated Canadian independent film scene. He had a charming turn as one of a small interconnected group of Toronto residents spending their last few hours on earth in 1998's "Last Night" (released in the USA in 1999), writer-director-star Don McKellar's take on the end of the world. Rennie, who won a Best Supporting Actor Genie for his performance, played Craig, a man who seeks to fit as many sexual experiences into his remaining time as possible. The character came off quite sympathetically in the acclaimed film, affably played by Rennie as a curious but decent man rather than an opportunistic lecher. He also teamed up with McKellar with a 1997-2000 stint on the CBC TV series "Twitch City" and had a small part in 1999's "eXistenZ", a thriller co-starring McKellar and directed by "Last Night" ensemble co-star David Cronenberg.