The interactive marketing and advertising arm of the Omnicom-owned Agency.com won the business following a pitch against four undisclosed agencies.
It will work with Heineken's online planning and buying agency, mdigital, to create the campaign.
The work, due to launch in April, is designed to complement the above-the-line launch campaign developed by Clemmow Hornby Inge.
CHI's campaign includes three TV spots that see a beer keg parachuted in from Holland that pleasantly surprises the lives of those around. It introduces the strapline "Premium 5% Heineken", and will run across media including television, outdoor, cinema and radio.
Heineken has tasked itraffic with producing a range of beer keg-themed rich-media eyeblaster executions, which float across the web page and are interactive.
The campaign will run across a range of high-traffic websites such as portals.
Itraffic joins Heineken's roster and will work for the brewer on a project basis.
Heineken is phasing out its Cold Filtered and Export variants in favour of the stronger 5% brand.
The lager is being launched as a direct competitor to the market leader, Stella Artois.
The above-the-line campaign is CHI's first work for Heineken since picking up the £10 million UK & Ireland account last year after Lowe resigned the business to work on Stella Artois.