Colman detailed their encounter while appearing on The Graham Norton Show when she was asked if she'd met any royals since playing Queen Elizabeth II in the drama.
"Yes, but it didn’t go very well," she admitted. "I met Prince William at a dinner and he asked what I was doing at the moment before he quickly added, 'Actually, I know what you’re doing.'
"I was so excited and asked, 'Have you watched it?' His answer was a firm, 'No.'"
However, it wasn't such royal embarrassment as the 45-year-old said the Duke of Cambridge was "very charming and lovely".
Colman has taken over from Claire Foy as the Queen for the third and fourth seasons of the Netflix hit, with season three set for release on 17 November.
While she may have not come face-to-face with the monarch since accepting the part, Colman has previously met the Queen.
Although, the Academy Award winner said she wasn't expecting a run-in with Her Majesty.
"I have accidentally met the Queen," she told Entertainment Weekly. "It was at a British Film Institute gathering to raise the profile of British film, independent film. We suddenly found ourselves, 200 people, in a big queue.
"I thought maybe we were going in to have some food. I hadn't read the order of the day. [I] looked around the corner, and there was the Queen and Prince Philip, and went, 'Oh! Oh no! I don’t know what to do!'"
She added: "I managed to remember what to say, sort of sticky-handed and bit sort of stumbly. That was it!"