Speaking at the annual Oscar Wilde party to honour the Irish in film, Kate said she believed the indie film would triumph over her movie The Reader, for which she is nominated for Best Actress.
"I think Slumdog is going to win best film most likely, but The Reader is in the same category and of course I have a secret hope," she confided.
"[But] I think that Slumdog Millionaire will probably win."
The British actress revealed that she is already very nervous about Sunday's big event, but has no special techniques to calm her pre-show jitters.
"There is literally nothing," she said.
"I've been through it before. I've tried everything.
"Sadly you can never fit a hip flask into those little bags unfortunately.
"I'm just going with the flow. It is a very exciting time and I just want to make the most of it and enjoy it."