"Been Jesse to your Rebecca for 30 years. 30 more, then that's it! I don't for one second take for granted your talent, your heart and most importantly, our friendship. Happy Birthday Lori, XO," Stamos captioned a throwback photo of him and Loughlin, smiling together on a boat.
Loughlin turned 54 Saturday.
Actress Andrea Barber, who played Kimmy Gibbler in the original sitcom and its followup, also shared kind words on social media for Loughlin on her special day.
"Happy birthday to my beautiful friend @loriloughlin, who has the best laugh, the prettiest smile, the funniest dog, and the biggest heart. I love you, Lori!" Barber wrote.