The line has vowed to preserve previously published itineraries "as much as possible".
Seven Seas Explorer will resume sailing from Venice from 16 October, taking over five of Seven Seas Mariner’s published cruises.
Mariner will go into dry-dock before resuming sailing from Miami on 18 December.
Seven Seas Navigator will also sail from Miami, starting 6 January 2022, with Seven Seas Voyager returning to service on 15 February 2022, sailing from Barcelona.
Seven Seas Splendor, meanwhile, will embark on its inaugural season on 11 September this year, sailing from Southampton.
