Members of the Rail, Maritime and Transport union (RMT) and Transport Salaried Staffs Association (TSSA) on Virgin Trains West Coast are taking action, with further 24-hour stoppages planned on December 22 and January 5, 8, 26 and 29.
Edinburgh is one of the biggest cities to be hit, with no Virgin West Coast trains serving the Scottish capital.
Virgin said it will run most of its West Coast services, although Chester and North Wales will not be served for most of the day.
Despite the suspension of services to Edinburgh, there will be a normal timetable on other routes, including London to Glasgow and London to Liverpool.
Virgin said it had offered a “significantly above inflation pay rise” which had been rejected by the unions.
Phil Whittingham, managing director for Virgin Trains on the west coast, said: “The RMT leadership is attempting to cause disruption when many will want to travel by train to spend time with loved ones.
“We have explored a generous 3.6% pay increase, however the unions’ leaderships are insisting on 4%, double the 2% average increase seen across the UK this year.
“We know how important it is for friends and families to get together over the festive season, so whilst we’re sorry for the disruption we will keep the majority of our trains running with fully-trained staff onboard and at stations.
“We remain open to talks with the RMT and TSSA, and urge them to call off these strikes which will cost their members pay for no gain.”
Passengers were urged to check before setting off and warned that services will be busier than usual.
TSSA leader Manuel Cortes apologised to passengers, but said the company had upset the workforce by awarding different pay rises to drivers.
“We’re obviously happy for the drivers that they have had a decent settlement, but our members believe that they too should deserve a little more than a stand still inflation pay rise.
“Passengers and staff are keeping Richard Branson up to his Necker Island in luxury, while they pay more for fares and work harder for less.”