"The night before, he was like 'Can you do my speech for me? I can't be there,'" the 29-year-old recalled.
"I was so panicked about his speech that I didn't even think about preparing one for myself."
Robbie continued: "I was up for two, for both films in my category, and it was not until I was in the car on the way there that I was like 'Oh my gosh, I hope I do not win because I don't have anything to say.'"
In a bittersweet turn of events, Laura Dern took home the coveted gong for her supporting role in Marriage Story.
But the actress' delivery of Pitt's speech proved a roaring crowd-pleaser courtesy of its Brexit and 'Megxit' jokes.
You could almost imagine the 56-year-old relishing the hilarious monologue unfold from home too with some pretty squirm-worthy quips making the cut.
"Hey Britain, heard you just became single, welcome to the club," the speech began, referencing Brexit. "Hope you get the best of the divorce settlement."
If that wasn't enough to see the starry crowd in fits of giggles, she continued: "He says he is going to name this Harry because he is really excited about bringing it back to the States with him."
"His words not mine", Robbie clarified, as the camera awkwardly panned across to Duke and Duchess of Cambridge who were sitting front row.
Thankfully, the royal couple laughed along too.
Robbie told fellow attendees that Pitt skipped the ceremony due to "family obligations" and it has since been reported that the father-of-six wished to spend time with his eldest son, Maddox.