Stamos shared video of the sweet proposal on Instagram, adding that "to assist with an engagement anywhere is an honor, but at @waltdisneyworld right as the fireworks began? That's magical! Congrats kids!"
"Will you marry me and make me the happiest man in the world?" asks the man, who has still not been named, while sweeping Disney music can be heard in the background. Stamos adds, "Please say yes!"
She did, much to the delight of Stamos and surrounding bystanders. Stamos then hugged the happy couple as he congratulated them.
A spokesperson for the actor told Entertainment Tonight that the man initially approached Stamos, apparently while shaking. When Stamos asked the man if he was alright, he said, "I'm about ready to propose to my girlfriend, will you help me?"
Stamos agreed, and the two lined up, looking like they were going to take a picture, so the man could propose. Before he could pop the question, the fireworks began, prompting the man to turn to Stamos and say, "You're John Stamos! What should I do?"
Stamos apparently leapt into action, getting his wife Caitlin McHugh and the surrounding crowd to turn on phone flashlights to shine a light on the man and his now-fiancée. McHugh also filmed the sweet moment.
Stamos has actually had some practice in Disney proposals: In 2017, he asked McHugh to marry him at Disneyland. The two later celebrated their honeymoon at Walt Disney World.
Stamos currently spends plenty of time with the Disney brand.
He's starring in a new Disney+ series called "Big Shot" and recently starred in "The Little Mermaid Live!" where he played Chef Louis. A sweet backstage photo shows him in costume alongside McHugh in an adorable mermaid outfit.
"Celebrating the success of #thelittlemermaidlvie with my favorite mermaid in the whole word @caitlinskybound!" he wrote at the time.
He's even spent time at Disney with "Fuller House" cast members Bob Saget and Dave Coulier.