The "Self Care" rapper died at the age of 26 in his home in Los Angeles on Friday, following a suspected overdose.
Taking to Instagram, Grande – who split from Miller in May – shared a simple black and white photo of the late star.
The 25-year-old singer chose not to add any caption to the post.
News of the rapper’s death came just a month after the release of his fifth album, Swimming, and weeks before he was due to head out on a world tour.
Miller – real name Malcolm James McCormick – and Grande started dating in August 2016.
He is said to have supported her through the aftermath of the Manchester terror attack – appearing on stage with the Dangerous Woman singer at the One Love benefit concert a month later – while she is said to have tried to help him with his addiction issues.
But they called time on their romance in May this year, with Grande later calling it a “toxic relationship” because of Miller’s use of drugs.
Within weeks, she had announced her engagement to the comedian and singer Pete Davidson.
“It’s strange,” Miller told Zane Lowe in his last interview. “Like, the whole thing is a little strange but it’s not negative. It’s just a part of something that’s going to continue to help make me who I am.
“You know, it’s all positive energy. I am happy for her and moving forward with her life just as I’m sure she is with me.”
Ms Grande is not the only person to honour the rapper, with tributes pouring in from a range of stars including one of his own heroes, Snoop Dogg.
“So sad u gone home young Mac,” the star tweeted. “Pittsburg we lost a real one today.”