The 72-year-old actress appears on Thursday's episode of The Ellen DeGeneres Show and confirms that she will not be attending the 33-year-old prince's nuptials.
When DeGeneres points out that she's met the royals on several occasions, Mirren recalls a funny moment she shared with Harry's older brother, Prince William. "I was at an awards thing or something, and William was presenting and he knew that I was in the room and he said, 'I've got to be really, really good because my granny is in the house," she reminisces. "So, he kind of knew who I was."
Mirren portrayed William's grandmother, Queen Elizabeth II, in the 2006 film The Queen, and won an Oscar for her role.
The Leisure Seeker star goes on to praise William and Harry, gushing, "They're both unbelievably charming, very straightforward, very charming, and a great credit to their father, [Prince Charles]."
DeGeneres also inquires as to what Mirren thinks of Netflix's The Crown, which is about the life of Queen Elizabeth and currently stars Claire Foy.
"I think it's incredibly accurate," she says of the series. "I think Claire Foy was brilliant. I sent her an email congratulating her. It was fantastic."
As for whether Mirren would ever consider joining the Crown cast, she insists, "No, because it's wonderful that I [portrayed Queen Elizabeth], it was wonderful that it was a success, but I didn't want [a] headline when I'm knocked over by a bus: 'The Queen Knocked Over by Bus.'"
She adds, "I wanted to kind of get away from that. I like to move forward, not back.
When DeGeneres compliments Mirren for embracing her age, the actress seems to think that she's 73 instead of 72. When the daytime talk show host confirms that she's is in fact 72, Mirren exclaims, "This is fantastic! This is amazing! I just made a whole year. Ellen, thank you."
DeGeneres quips, "You look great, but you're losing it."
While Mirren says has no intention of ever retiring from acting, she does admit that she almost always wants to just "stay at home and watch TV." As for her favorite shows, she's loving HBO's Silicon Valley and Netflix's Stranger Things.
Mirren may not want to star in The Crown, but Helena Bonham Carter is rumored to be on board. ET chatted with the cast of the beloved show at the Golden Globes about the casting report.