"Happy birthday Hef!!" the Girls Next Door alum captioned the snap. "Thank you for EVERYTHING. People might not understand you but that's because they've never had the chance to know you like I do. I'll celebrate you forever!!!"
Also chiming in with birthday wishes was Hef's 25-year-old son, Cooper, who shared a shot of his father wearing his trademark silk smoking jacket and captain's hat.
"To the guy who is smart enough to create a job that allows him to roll out of bed in pjs and go straight to work," Cooper wrote. "Happy birthday Dad. I love you."