The rail operator will hold a statutory review for the account, which is held by Vizeum, by the end of the year.
Vizeum has worked on Eurostar since 2005, when it won the business in a pitch against then incumbent Manning Gottlieb OMD and MEC.
Fallon, which was appointed in 2007, continues to handle UK advertising for Eurostar and recently created a TV campaign using the line "exploring is beautiful".
Separately, Eurostar has asked Fallon, TBWA\Brussels and the Paris-based Leg to pitch for an advertising project to support its official sponsorship of the 2012 London Olympic Games.
Emma Harris, the director of sales and marketing at Eurostar, said: "We are very happy with our relationship with Vizeum, they are very much part of the marketing team. It’s just a procurement review as we have finished our four-year cycle with the agency and we are being pushed towards a tender."