The "Nothing Breaks Like a Heart" singer showered her "best friend" with birthday wishes on her Instagram Story on Friday and Saturday. Sharing black-and-white photos of the 23-year-old, Cyrus praised him for being by her side.
"Happy birthday to my best friend in the entire world @codysimpson," she wrote. "I love you and our pirate life."
She then proceeded to post a video of them wearing fase masks and hugging. "Happy birthday to my favorite human to get weird with on the entire earth," Cyrus posted, along with "I love you."
Throughout the day, Cyrus continued to share photos of her "baby" on his "bday."
Simpson, on his end, celebrated his 23rd birthday in Milan, Italy. He attended a variety of fashion shows, sharing moments on his Instagram.
He also was surprised with a birthday cake during dinner.
Simpson and Cyrus have been celebrating their birthdays and holidays together ever since her split from Kaitlynn Carter and Liam Hemsworth.
Fans started speculating that Simpson and Cyrus may have gone their separate ways just days before Christmas, as Simpson was spotted in New York City with Playboy model Jordy Murray. Simpson's agent confirmed to ET that the couple had not broken up, saying, "There is absolutely no truth to this story. Cody went out with a friend and all the rest is fabricated. Period." His sister, Alli Simpson also told the Daily Mail Australia, "Yes, [they're] together for sure."
Meanwhile, Cyrus reached a divorce settlement with Hemsworth last month.
For more on Cyrus and Simpson, watch below.