Eurostar comms director Paul Charles said Consolidated, which won a two-year brief worth around £500,000, would help woo travellers from outside the South-East.
A key message will be the average 20-minute cut in journey times to Paris once the high-speed route from St Pancras is completed.
It will also communicate the station move itself, and Eurostar's claimed punctuality improvements and environmental benefits over short-haul airlines. The agency will plan events and meetings with stakeholders, including other train operators, MPs and the public.
Consolidated won the contract after a four-way pitch. The account will be managed jointly by directors Paul Davies and Chris Lawrence.