ScotRail guards based at Glasgow Central station will strike every Sunday between 29 November and 3 January, in a dispute over bosses' abuse of disciplinary procedure.
The strikes are accompanied by a ban on overtime, rest day working, and higher grade working from 30 November to 2 January.
RMT says ScotRail has used company disciplinary policy in a punitive way. A union statement said: "We will not tolerate these continued attacks on the Conductor grade and to bring an immediate stop to the punitive disciplinary action against our members."