The agency has been tasked with promoting cycling through a series of major events over the summer after winning a pitch.
These include TfL’s existing Barclays Cycle Hire Roadshow and a new roadshow set to take place during major events such as Tour de France and Tour of Britain.
The push comes as Greater London Authority figures indicate that the amount of cycling done in the capital is up 173 per cent since 2001 and as accidents continue to raise concerns over its safety.
In December, London Mayor Boris Johnson promised to continue what he dubbed a "cycling revolution" and pledged to make 33 of the city’s most dangerous junctions safer.
Rikki Butler, Grayling account lead, said: "London cycling has considerably increased since 2001 – we are really excited to be working with Transport for London to harness this enthusiasm and get even more Londoners cycling more often and more safely.
"Our innovative cycling roadshow will capture the attention of cyclists and non-cyclists alike. It will be designed not just to entertain visitors but to have a wider impact on the behaviour of cyclists and potential cyclists. We want to ensure people are provided with the information and tools needed to overcome barriers to cycling in London."
Work will last until late autumn and involve both organising and promoting the events. It will be handled by Grayling Engage, a specialist unit that focuses on consulting with stakeholders and the public.