Adiga's book The White Tiger, a tale of two Indias, tells the story of Balram, the son of a rickshaw puller in the heartlands, one of the 'faceless' poor left behind by the country's recent economic boom.
It charts his journey from working in a teashop to entrepreneurial success.
The other shortlisted authors were Australia's Steve Toltz, with A Fraction of the Whole, Irishman Sebastian Barry for The Secret Scripture, and British writers Linda Grant and Philip Hensher for The Clothes on Their Backs and The Northern Clemency respectively.
A total of 41 books have won the prize since it was launched in 1969, because the award was shared in 1974 and 1992. Contenders must have been published in the past year and originally written in English.
The award, which honours the best fiction written in English by an author from the UK, Ireland or the Commonwealth nations, was handed out at the Guildhall in London.
The win means Adiga can expect an upturn in sales and added recognition.
Image: Adiga poses for pictures with his book The White Tiger at a photocall in London.
Photograph: Leon Neal/AFP/Getty Images
Buy Steve Toltz's A Fraction of the Whole on rediff.com