Flexible fares lead in from £39pp one-way and will be available until the end of the year, building on the flexibility offered to those with existing bookings.
It comes as Eurostar prepares to restart Dutch services later this month, and Disneyland Paris services in August.
From 9 July, Eurostar will resume London-Amsterdam and London-Rotterdam services from St Pancras, with fares from £40pp; alternative destinations accessible via short onward connections include Utrecht, The Hague, Haarlem and Delft.
Return journeys will continue to operate via Brussels for passport checks and security screening.
Services to Marne-la-Vallee, serving Disneyland Paris, will resume on 2 August, with fares from £39pp one-way, allowing families to travel to the resort in around two-and-a-half hours.
Fares will go on sale on Thursday (2 July) for Christmas, with bookings available through to 31 January 2021.
New hygiene measures in stations and onboard Eurostar services include a new seat map to ensure social distancing; deep cleans after every journey, and an increase in onboard cleaning routines during journeys; and a requirement for passengers to wear masks onboard and in stations.
