Loughlin, 54, shared the cute clip with Stamos on Instagram on the actor's 55th birthday Sunday.
The video shows the Fuller House stars singing along to the Frozen song "Love is an Open Door." Loughlin wished Stamos a happy birthday in the caption.
"Happy Birthday @johnstamos it's been 30 years of laughter, fun and finishing each other's .... sandwiches. Here's to 30 more," the actress wrote.
"Have a beautiful day with @caitlinskybound & your pride and joy, Billy!!" she added, referencing Stamos' wife, Caitlin McHugh, and 4-month-old son. "Love you buddy. #fullerhouse #fullhouse."
Stamos had shared a similarly sweet message on Loughlin's birthday in July.
"Been Jesse to your Rebecca for 30 years," he wrote, referencing their Fuller House characters. "30 more, then that's it! I don't for one second take for granted your talent, your heart and most importantly, our friendship."
Loughlin and Stamos played Aunt Becky and Uncle Jesse on the ABC sitcom Full House, which had an eight-season run from 1987 to 1995. The pair reprised the married couple on Fuller House, which was renewed in January for a fourth season on Netflix.