Avanti West Coast staff will go on strike on New Year's Eve and several January dates in a row over rest days.
The Rail, Maritime and Transport union said its members working as train managers will strike on New Year's Eve, January 2 and Sundays between January 12 and May 25.
An RMT spokesperson said: "Our members have resoundingly rejected Avanti's latest offers in two referendums and sustained strike action is now the only way to focus management's minds on reaching a negotiated settlement with the union."
The RMT said up to 400 of its members are involved in the dispute.
They voted by 83% against a suggested deal.
Avanti said it was looking at how the strikes will impact services and will confirm its plans as soon as possible.
Strikes planned for December 22, 23 and 29 were suspended last week after a suggested agreement was put to a referendum of RMT members.
An Avanti West Coast spokesperson said: "This strike action will cause significant disruption to our customers making journeys on the West Coast Main Line over an extended period.
"We're disappointed our train managers who are RMT members have voted to decline the very reasonable, revised offer made to them to resolve the rest day working dispute and avoid inconveniencing our customers.
"We remain open to working with the RMT to resolve the dispute."
Avanti West Coast runs several routes on the west side of the UK, including from London Euston to Manchester Piccadilly.
Other services go from London to Glasgow, Edinburgh, Blackpool, Liverpool, Holyhead, Birmingham and Wrexham.