Weiss, who won the prize for outstanding directing of a variety special for his work on the Oscars, surprised his girlfriend Jan Svendsen with a proposal as he accepted his award at the Microsoft Theater in downtown Los Angeles.
"You wonder why I don't call you my girlfriend? It's because I want to call you my wife," he said, as she gasped, then rushed on stage.
"This is the ring my dad put on my mom's finger 65 years ago," he continued, holding it up. "I want to put this ring that my mom wore on your finger in front of all these people ... will you marry me?"
She accepted while the stunned audience looked on.
Weiss had just lost his mother two weeks before.
Backstage, he was asked what he would have done if he hadn't won.
"Wait until next year?" he quipped, before adding that his backup plan was to propose at In-N-Out Burger.
"This was coming," Weiss added, turning to Svendsen. "The timing just lined up very nicely. ... Thank you for saying yes."
"I never expected this, I was shocked," Svendsen said. "Thank you for not playing us off!"