Adify, which already has agreements in place with 140 publishers worldwide, including Guardian.co.uk and Reuters, has been trialling campaigns for FT clients with brands including Royal Mail.
Adify will provide the FT with the technology to enable advertisers to reach SMEs via niche partner websites.
Jon Slade, the Financial Times' global online and strategic advertising sales director, said: "The FT partner sites proposition will allow clients to tap into a larger targeted audience in popular niches, complementing the inventory that already exists on FT.com."
"Audiences are becoming increasingly fragmented online and our clients will now benefit from being able to quickly access inventory on smaller specialist websites, hand-selected by the FT, via a single point of contact."