The win is Five's largest ever non-sport commercial deal and includes 72 hours of sponsored programming.
Five plans to broadcast a regular weekly poker slot at midnight for the next 12 months from mid-December, along with events including the PartyPoker.com European Open and the Party-Poker.com World Open.
The programmes will be promoted on-air and on Five's website. Five will also work with PartyPoker.com in the development of its own website, www.five.tv/poker.
Jonathan Lewis, Five's head of commercial development, said: "We realised very early on that poker programming was significantly outperforming average audience levels in the late night slot. We also saw the huge emergence of the online sector and were able to capture this in one overall deal."
Five has agreed poker programme deals in the past with other online operators, including Pokerstars.com and European Poker Tour, and more recently scheduled the UltimatePoker.com Showdown.
PartyPoker.com is the world's largest online poker website, with more than nine million registered players, and recently floated on the UK stockmarket at a value of 拢4bn.
Meanwhile, Five has acquired two hit US shows after buying the terrestrial rights from LIVINGtv. Grey's Anatomy, a medical drama, which launched on Living in August, focuses on the lives of five medical interns struggling to form friendships and relationships in the stressful environment of hospital life. It will be transmitted on Five next year.
The other is Criminal Minds, featuring an elite squad of FBI profilers who analyse the country's most twisted criminal minds. It will air on LIVINGtv in early 2006 and on Five later in the year.
Dan Chambers, Five's director of programmes, said: "I am delighted that we have been able to acquire two top-rating US shows. We have a reputation for the finest America dramas and these series will make great add-itions to the channel."
They join other US imports such as Law & Order, The Shield and Joey, in Five's line-up.