
Hicks will be responsible for building relationships with TV, VoD and online buying teams. Before joining Tremor, he worked in various sales positions at ad networks Videoegg and E-Type.
Dorey's role as publisher development director will be to establish Tremor's publisher network in the UK. Dorey previously worked at Hapax Ltd and has five years' experience in online business development.
Littlejohns joins Tremor from the online network arm of a commercial TV channel.
Tremor Media launched in the UK in December 2008 under managing director Adrian Lacey. Lacey previously worked at advertising behavioural targeting specialists TACODA.
Lacey said this was a "critical period" for Tremor UK, and it had been vital to assemble key strategic employees as quickly as possible, so Tremor could take its message out to the market and start winning business.