Deadline reports Vallée is believed to have died from a heart attack on Christmas Day (December 25) while preparing to host guests the following day at his riverside cabin outside of Quebec City, according to multiple sources.
The Montreal native began his career making short films and made his feature debut with Black List in 1995, before achieving breakthrough success with the 2005 film C.R.A.Z.Y., which won four Genie Awards in Canada including Best Picture, Screenplay and Director, according to Deadline.
Vallée directed several more films before Dallas Buyers Club, a biographical drama based on Ron Woodroff — a Texas electrician who was diagnosed with AIDS and given a month to live — starring Matthew McConaughey.
The film won Oscars for both McConaughey (Best Actor) and Jared Leto (Best Supporting Actor), while also being nominated for Best Picture.
Valée later turned his attention to television, beginning with the critically acclaimed Big Little Lies in 2017.
The HBO drama won eight Emmys including Outstanding Limited Series and Outstanding Directing for Valée, who also won the DGA Award for Outstanding Directing for the series.