All CrossCountry trains in Scotland will be cancelled on Sunday in the first of a series of strikes that also threaten Christmas services.
The operator said none of its trains would run north of York, affecting services to and from Aberdeen, Glasgow and Edinburgh on the east coast main line.
Around 25 trains will be halted, include services to the Midlands and the south-west England.
Further strikes by the Rail, Maritime and Transport union (RMT) have been called for Sunday 26 November, Saturday 9-Sunday 10 December, Christmas Eve and Hogmanay.
CrossCountry described the timing of the strikes as "extraordinary".
However, it said it would not know whether the other strikes would have the same impact on services until nearer the time.
The RMT said the dispute among train managers and senior conductors - or train guards - was over "abuse of rostering and Sunday working".
It accused Arriva, which runs the firm, of "wrecking" talks this week.
General secretary Mick Cash said: “It is disgraceful that the management at Arriva effectively sabotaged talks on Wednesday that were making progress towards a settlement to this dispute.
"Our members are standing up for the principles of a decent work life balance and against the abuse of rostering and Sunday working by a management that is out of control."
CrossCountry said Sunday's walkout would "significantly" affect CrossCountry train services.
It said it would operate a reduced service between 9am and 7pm using some longer trains.
It said: "With fewer trains available we expect all our services, and any replacement bus services, to be very busy."
A spokesperson for CrossCountry said: “It is disappointing the RMT is calling for its members to strike when we have already held extensive talks and feel that both sides recognise how this can be resolved without causing disruption to rail users.
“To call for six days of strikes before the New Year is extraordinary and will significantly disrupt our customers’ journeys and place a heavy burden on our staff as we approach the Christmas holidays.
"We urge the RMT to call off these strikes and allow talks to continue.”