The 38-year-old makes her big-screen comeback in the title role in the Disney film of the same name, four years since action thrillers Salt and The Tourist, as she has been focused on directing.
The two-time Oscar-winning actress, wearing a black beaded billowy dress by Versace, was joined on the rain-sodden blue carpet by fiance Brad Pitt and their eldest son Maddox at the preview of a special costume exhibition at London's Kensington Palace.
"What isn't there to like about Maleficent? She was my favourite when I was little. I wasn't into princesses and I thought she was so elegant and so powerful," she said.
"She scared me a little bit, but I think it's a natural thing for children, and everybody to want to understand their fears and to get closer to those things - the shadows, the dark and what frightens us - so I was always curious."
Jolie continued: "And then I read the script. It's such a beautiful script. It was very moving and it helps you understand that things are not black and white."
Maleficent, which also stars Lesley Manville, Juno Temple, Imelda Staunton and Sharlto Copley, opens on May 28.