Brown will be an RFA at the end of the deal in 2020.
Brown was a plug-and-play piece for Leafs head coach Mike Babcock in 2016-17. The 23-year-old rookie posted solid secondary production, played in all situations, and showed an impressive level of overall maturity to his game.
The Toronto native started on the fourth line in October but quickly earned a promotion onto the shutdown unit with Nazem Kadri and Leo Komarov (after Milan Michalek was sent to the minors in October) where he was trusted on the ice against the best players in the league.