The Duke meets actors James Nesbitt, Richard Armitage and Aidan Turner
His Royal Highness joined the stars of The Hobbit: An Unexpected Journey for the screening in Leicester Square, London.
The Duchess, whose pregnancy was announced last week, continued to rest at St James's Palace as she is suffering acute morning sickness.
The Duke walked down the special "green carpet" which replaced the usual red for the night, and went inside the Odeon building to meet the cast and director Sir Peter Jackson.
A host of stars attended the first UK performance of the latest JRR Tolkien adaptation included Cate Blanchett, Spooks star Richard Armitage and Sherlock actor Martin Freeman who plays Bilbo Baggins.
The trilogy of films, based on the novel by Tolkien, all directed by Sir Peter Jackson, are set in Middle Earth 60 years before the Rings trilogy.
The royal film performance was being held in aid of CTBF, which supports film and television industry employees and their families in times of hardship.
His Royal Highness was also presented with a Hobbit goodie bag to take home to his wife.