Poppy Shute joins the Sledge team to work on the O2 conference and experiential events account – which the agency won in December.
Shute is the latest addition to the O2 team following the appointment of Samantha Golding as account director in March.
Meanwhile, Sledge will move to offices in Shepherds Bush from its headquarters in Camden on Monday (11 July).
The agency is "returning to its roots", said senior account manager Karen Swift, after spending two years in Camden.
Sledge chief executive Nic Cooper set up the business in 1991 but sold it to Australian company Photon Group in 2007.
The team moved from Shepherds Bush to offices in Camden in August 2009, before Cooper bought back the agency in December.
Swift said: "From a business point of view, it was obvious that we were quickly outgrowing our Camden offices with the expansion of our digital and video offering and also off the back of winning some key new business projects for which we will be looking to welcome some new recruits."
Sledge currently has around 20 members of staff, who will move to the base in Millers Way, Shepherds Bush.