West Midlands Railway chiefs issued the warning with a "very limited timetable" implemented this Friday and Saturday, then on November 7 and 9.
It coincides with the start of Birmingham's popular Frankfurt Christmas market which starts on Thursday and is expected to see crowds of people flock to it.
Transport Salaried Staffs' Association (TSSA) members will strike on Friday, while National Union of Rail, Maritime and Transport (RMT) staff will strike on other dates.
Jonny Wiseman, West Midlands Railway customer experience director, said: "It is disappointing that our passengers’ journeys will again be impacted by industrial action over the next week.
"A very limited timetable will be in operation on strike days and we are urging passengers to only travel if absolutely necessary.
"The action coincides with the opening of the popular Christmas market in Birmingham and I am urging anyone attending to plan their travel carefully as rail services will be extremely limited."
A very limited timetable will be in place on all of the strike days, with no services running after 7.30pm. Two trains will run per hour on the Cross-City Line from Redditch/Bromsgrove to Birmingham New Street, with one train from Wolverhampton to New Street and one from New Street to Birmingham International per hour.
No trains will run on any other West Midlands Railway route, including all routes via Birmingham Snow Hill, Birmingham-Shrewsbury, Birmingham-Worcester-Hereford and Nuneaton-Leamington Spa.
Late night and early morning services may be subject to amendments on days either side of industrial action including this Thursday, Sunday, November 8 and November 10.
For more information visit wmr.uk/industrialaction