Run by British Council Performing Arts Entrepreneur of the Year Alex Fleetwood, the company is launching 99 Tiny Games at the event, which runs alongside the Olympics.
Ladbury won the work, which will extend beyond the festival, following a pitch process in what was the first retained brief put out to tender by Hide&Seek.
The agency has been brought in to encourage more people to play by moving away from getting coverage in niche press and targeting consumer national and international titles.
The two agency partners, Rebecca Ladbury and Pavla Kopecna. will be leading the account.
Ladbury said: ‘We have a wealth of experience at Ladbury PR publicising UK and international games, in particular where they have something special to offer, be it an educational or creative element that makes a game that little bit more compelling.’
She went on to add: ‘We aim to help Hide&Seek take games out of the niche press into mainstream media and put the essence of play back into people's lives.’
The 99 Tiny Games project will include 99 street specific games to be played across the capital.