Some sailings between Hull and Rotterdam have been cancelled due to one of the two ferries on the route being out of service.
In an email to passengers seen by the BBC, P&O Ferries said the Pride of Rotterdam vessel was delayed returning from its annual refit.
The company said it would not return to operations until 19 February.
The ferry and its sister ship the Pride of Hull run a nightly two-way service between the city and the Dutch port.
In its email, the company said customers could book an alternative date or get a refund.
It added: "We do apologise for any impact that this may have and hope that this information allows you to plan ahead."
In a statement, P&O Ferries said: "The Pride of Rotterdam is currently undergoing routine maintenance as part of her scheduled annual check.
"All customers that have been impacted by this have been contacted by email. We expect sailings to resume normal service soon and will keep customers updated."