The drama, which airs on The CW network in the US, has been a smash hit with its stories of brooding vampires, drugs, drinking and sex.
The show, sold to ITV by The CW parent Warner Bros, is not due to be broadcast on British television until February, but episodes are being made available while it is still airing in the US as part of an effort to fight online piracy and satisfy fans of the L J Smith-written books on which the series is based.
Josh Berger, president and managing director, Warner Bros. Entertainment UK, said: "We're committed to providing our shows with the best possible launch platform. This highly innovative approach to releasing 'The Vampire Diaries' gives us and ITV2 the chance to maximise excitement ahead of its UK premiere in February, and provides consumers with a high-quality legal alternative to pirated versions."
The first episodes will be made available this Friday at a standard price of £1.89 and £2.49 for the high definition version. The show is only half-way through its 22-episode run in the US having debuted on September 10.
'The Vampire Diaries' tells the story of two vampire brothers - one good and the other bad - as they compete for the attentions of a high school girl Elena Gilbert (played by Nina Dobrev). Elena, like Bella from 'Twilight' and Buffy from 'Buffy the Vampire Slayer' before her, has to deal with teenage life in a town where supernatural events takes place.
The show is The CW's best performing series and was given the go-ahead for a full, 22-episode first season, a strong indication that it will be back for a second year.
Adapted for the small screen by Kevin Williamson of 'Scream' and 'Dawson's Creek' fame the show appears to echo the smash hit 'Twilight' vampire movies from the books penned by Stephenie Meyer, but LJ Smith's books came first.
The show joins ITV2 a growing cast of US dramas airing on ITV2 and available on ITV's iTunes store including 'Gossip Girl', 'Supernatural' and 'Entourage'.
Zai Bennett, director of digital channels and acquisitions, ITV, said: "Recent hits such as 'Gossip Girl' have demonstrated how new entertainment brands can be fuelled by the passion of early adopters.
"By making 'The Vampire Diaries' available in the ITV2 area on iTunes we're feeding the appetite for brand new US content and helping to spread the word about a show we're incredibly excited about."