The deal follows a review by Prudential of existing network activity and a formal pitch process that was led by RBS head of category marketing, commercial and intermediaries, Chris Bottle.
Buy.at will manage a range of search engine optimisation affiliates for Prudential, including loyalty sites and niche content affiliates in the motoring world. Affiliates will be paid commission, starting at £55 for each sale they generate.
Buy.at will link the affiliates to facilitate cross-selling.
All of the activity will be analysed using Buy.at's management tool, which shows overall activity as well as details such as sales per region, per affiliate or per product.
Kevin Cornils, chief executive of Buy.at, said: "Prudential offers preferential prices for niche risks, so we can work with a wide range of affiliates and offer incentives to boost performance at key times of the year."
The news follows the announcement last month that Buy.at's parent, AOL's Advertising.com, hired Cornils as its new UK managing director, as the company looks to restructure its UK operation.
Other Buy.at wins include the consolidated affiliate marketing contract for supermarket chain Asda.