The agency will work with Expedia on building its presence through brand partnerships, guerrilla marketing and other activity.
Media owner sources said Naked was in the process of developing a series of proposals for the Expedia brand that would move it into new areas.
Naked's appointment does not affect Media Planning Group's hold on Expedia's media planning and buying account.
Creative for Expedia is handled by Clemmow Hornby Inge, with which Naked recently launched a joint venture, Naked Inside. However, sources said it is the main Naked agency, not Naked Inside, that has been selected to work with Expedia. CHI's creative work has included TV, radio, press and outdoor.
No-one at either Naked or Expedia was available for comment.