"Welcome to 40 baby. I've celebrated 18 birthdays with you, and I can say it's amazing growing up with you," he wrote alongside a series of photo featuring himself and his wife through the years. "The person you have grown into is inspiring. You have become a successful business woman, superstar, dedicated mother, Philanthropist, supportive wife, wine maker, motorcycle mama, and amazing friend to all around you."
"I'm so proud of the woman you have become, and you are more beautiful than ever," the 44-year-old former motorcross competitor continued. "You truly are like wine. You just keep getting better, and I'm so lucky to be along on this crazy ride with you. I love you baby. Looking forward many many more birthdays with you. I can't wait to see how nuts you and I are in our 80's 😂😂. Enjoy your day."
Fellow celeb, Selma Blair, also chimed in, offering the songstress a thoughtful message: "Happy birthday. You have settled in my soul as the embodiment of living a well fought for life, an amazing mom and wife and human. I love you. Happy happy birthday."
Pink herself shared some birthday wishes, as well as a response: "THANK YOU FOR MY BDAY WISHES. I’m jumping for joy to be 40. I’m so f’ing into it. I love you all!"
In April, Pink appeared on the Today show, where she spoke with Carson Daly about the challenges of her marriage and how she and Hart make it work.
"Carey and I have been in couple's counseling almost our entire 17 years we've been together. It's the only reason we're still together," she stated.
"He speaks Polish, I speak Italian and she [our therapist] speaks both. We do not speak the same language," she later shared. "...We come from broken families and we had no model of how are we supposed to keep this family together and live this crazy life? And there's no model. There's no book that says, 'Here's how to do this.' So we go to counseling and it works."
In the past, Pink has also shared how much of a creative influence Hart is on her and her work.
"[Carey] is totally my muse. We have been together for 17 years and it is work but it's worth it," she told ET in February at her star ceremony on the Hollywood Walk of Fame
She added: "He got me flowers yesterday which never happens, so that's what made today sort of set in... that this is a big deal. It was sweet."
See more on Pink below.