There was no competitive pitch for the business, as Unanimis already works with Five on its sites.
Unanimis will now represent these two Five channel sites for online advertising, which means the sales house now represents Five.tv and all associated programming sites.
Other programming strands on the site include the microsite for American import Prison Break, which has doubled the advertising inventory on Five.tv, according to Unanimis.
Five launched its video-on-demand service, Five Download, beginning with episodes of CSI, in October. It partnered with BT Media and Broadcast to develop the service, as part of the Five.tv website.
Last week, Media Week revealed that Unanimis had hired rival AdLink's commercial director, Lee Puri, to the newly created position of business development director.