Miller, whose real name is Malcolm McCormick, had faced a continued battle with drug addiction.
Miller's most commercially successful album was his 2011 Blue Side Park which topped the charts.
His good friend and fellow Pittsburgh rapper Wiz Khalifa tweeted, "Praying for Mac's family and that he rest easy". His 2016 album, "The Divine Feminine", charted at number 2 on the Billboard 200 and featured guest appearances from Kendrick Lamar, Anderson Paak, and Ariana Grande.
Born in Pittsburgh, Miller got his first record deal in 2010.
Last month, Miller released his fifth studio album "Swimming" and was scheduled to begin his US tour in October.
Mac Miller and Ariana Grande perform on stage, June 4, 2017, in Manchester, England for the "One Love Manchester" benefit concert. The singer tweeted, "I have cared for him and tried to support his sobriety & prayed for his balance for years (and always will of course) but shaming/blaming women for a man's inability to keep his s**t together is a very major problem". After they split in May, he wrecked his auto and was later arrested for DUI and hit-and-run. Just last month, the Los Angeles Attorney's Office officially charged the rapper with a DUI stemming from a auto accident in May in the San Fernando Valley.
Chance the Rapper, Khalid and Shawn Mendes swiftly paid tribute on Twitter.
This is a breaking story and will be updated.