Travellers to Paris and Brussels were deterred after major terror attacks in November 2015 and March 2016 and numbers fell by 4% to 10 million.
Eurostar, whose main shareholder is the French national rail operator, SNCF, made a profit of 31m euros in 2015.
It said 2016 had been "a difficult year".
Revenues were down 3% at Â£794m.
But the company said there had been a pick-up in business at the end of last year which had continued into 2017.
Last year, Eurostar said it would cut some of its services from December as it introduced longer trains.
The new e320 trains introduced earlier in 2016 have around 20% more seats than the previous model, and are used for most services between London and Paris.
The channel tunnel train service Eurostar said it made an operating loss of 28m euros (Â£25m, $30m) in 2016 following a drop in passenger numbers.