Miller, whose real name was Malcolm James McCormick, had struggled with substance abuse in the past.
The rapper Mac Miller has died at his home in the San Fernando Valley in California on Friday.
His death comes several months after he ended a high-profile, two-year relationship with pop superstar Grande, often seen as the inspiration for his songs.
"I just wanna go on tour", he tweeted on Thursday.
Mac had always been open about his struggles with substance abuse in his music, in particular his largely autobiographical 2014 mixtape, Faces.
Chancelor Bennet, better known as Chance The Rapper, said they were good friends and helped him to launch his career.
Right now, Grande is having to process the news that someone she spent two years of her life with, trying to support and keep sober has passed away.
Once the reports of Miller's death hit social media on Friday, those around the sports world were the first to react. "We join all of his fans across the globe in extending our thoughts and prayers to his family and friends". He reportedly signed his label to Warner Bros Records for some $10 million.
Several months ago, Miller wrecked his vehicle, and he was also arrested for a DUI and hit and run.
Now, an insider tells ET that the singer is absolutely "devastated" by the tragic death.
"He was one of the sweetest guys I ever knew, "the rapper wrote on Twitter".
The album included the song Come Back to Earth, with Miller trying to chart his way through tough times: "In my own way, I feel like living some alternate reality/And I was drowning, but now I'm swimming through stressful waters to relief". "I really am. I know what actually happened in reality, and that's enough for me".
"I like that he incorporated Pittsburgh so much into it", said Arielle Pierce, a fan. He also performed with her at her One Love Manchester benefit concert later that year.