The trial is believed to be a first on a public sector organisation's website and will include Yell.com content placed on high-traffic, relevant pages of the through Yell.com netReach, which will deliver geographically relevant content onto the TfL site.
A second phase of the online sponsorship deal will include an interactive Yell.com banner, with in-built search functionality, introduced onto TfL's homepage.
The decision to deliver content from Yell is part of a wider partnership with the international directories publisher, which started with the inclusion of Transport for London content within Yellow Pages directories in 2005.
Giles Bailey, TfL's head of group marketing strategy and integration, said: "The trial sponsorship partnership between Transport for London and Yell.com is a good fit for both parties and will add useful functionality for our passengers.
"There are more than 7m visits to tfl.gov.uk every month, and this trial will help us appraise the potential revenue generation opportunities for TfL as we consider online sponsorship offerings. This is revenue that will be ploughed back into improvements to the capital’s transport system."
Ian Bowen-Morris, head of advertising syndication at Yell.com, said: "We are delighted to deepen our partnership with Transport for London, and are confident that Yell.com netReach will provide TfL's website visitors with relevant, trusted content which will be extremely useful to them.
"As well as the forthcoming interactive banners, we have also added links to TfL's Journey Planner on Yell.com's London location pages. In the future we hope to collaborate more closely to integrate functionality between the sites, adding value to both sets of website visitors."
Transport for London said it would analyse the commercial viability of continuing to allow online sponsorship, as well as customer reaction, before taking the option further.