Under the alliance, passengers can book AirAsia and AirAsia X flights on the Expedia website. Previously, passengers wanting to fly on the airline could only book on the its website.
AirAsia is Southeast Asia's largest budget carrier, while Expedia is the world's biggest online travel company by revenue.
"There is a lot of focus on travel in Asia today and this collaboration allows our customers to connect to a great network here via AirAsia," Expedia chairman Barry Diller told a media conference in Singapore.
"This is particularly exciting, given Asia's influence in the online travel marketplace."
AirAsia founder and group chief executive Tony Fernandes said the venture was another step forward for the region's booming travel market, especially in the online segment.
"This partnership between two global brands and leaders in the travel industry comes at a time when online travel bookings are exploding in the region," he Fernandes.
AirAsia X is a long-haul affiliate of AirAsia and Richard Branson's Virgin Group.It flies to 14 destinations -- London, Taipei, Tehran, Paris, Seoul, Tokyo, China (Tianjin, Hangzhou, Chengdu), Australia (Gold Coast, Melbourne, Perth) and India (Mumbai, Delhi).