Santa Claus will meet children on the flight and hand out gifts.
The campaign is supported by an online film which captures reactions of passengers as Captain Claus appears from the cockpit.
The work has been created by VCCP and PR agency Taylor Herring.
Tina Milton, head of cabin crew at easyJet, said: "We fly millions of people home or on holiday over the Christmas period and we want to get the festive feeling started on board.
"We have hired the world’s most famous pilot to fly on over 100 selected flights and give over 20,000 passengers an incredible surprise."