The No Tears Left To Cry singer, 25, posted a captionless black and white photograph of Miller looking up at the camera on her Instagram account, which has also had the comments disabled.
Grande and Miller dated for around two years before breaking up earlier this year.
Shortly after they parted ways, Grande responded to a fan on Twitter who criticised her for dumping him and said their relationship had been “toxic”.
She tweeted: “I am not a babysitter or a mother and no woman should feel that they need to be. 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*** together is a very major problem.”
She also later said she and Miller shared “unconditional love” and that he was “one of my best friends in the whole world”.
Miller performed with Grande at a memorial concert following the 2017 Manchester Arena bombing and the pair released music together before their split earlier this year.
The LA coroner said the cause of Miller’s death is yet to be determined and that a post-mortem examination will be carried.
In a statement, his family said Miller was a “bright light in this world for his family, friends and fans”.
Ed Sheeran, Drake, Chance The Rapper and Post Malone were among a stream of stars to pay tribute to the “great talent”, who released his fifth studio album, Swimming, in August.
Posting an image of the pair on Instagram, Sheeran said Miller’s untimely death was “so heartbreaking”.
He said: “I hung out with Mac a few times over the years and he was always such a sweetheart, always had the time of day for anyone, whoever they were.
“As well as being a great talent, he was a great human.”
Snoop Dogg, who appeared in Scary Movie 5 with Miller in 2013, said he was “so sad”.
Post Malone said Miller “changed so many lives”, while Chance The Rapper said he was “one of the sweetest guys I ever knew”.
Jaden Smith tweeted: “Long Live Mac Miller, Rest In Peace We Love You,” while Drake wrote “rest easy Mac” on Instagram.
Less than 24 hours before his death, Miller had spoken of his eagerness to go on tour and play his new material for fans.
“I wish it started tomorrow,” he said on Thursday.
However the musician, whose break came with releasing mixtapes in his late teens, had recently spoken of the burden that fame brought him.
“A lot of times in my life I’ve put this pressure to hold myself to the standard of whatever I thought I was supposed to be, or how I was supposed to be perceived,” he told the New York magazine’s Vulture website.