It said there would be an unspecified number of cancellations daily and urged passengers to check before travelling.
The union’s move as part of a long-running pay dispute follows a one-day strike on Monday which reduced ScotRail services to just three routes in its greatest disruption this year.
It told The Scotsman that notice would be served on ScotRail on Friday of further 24-hour strikes, to “up the anti”.
The overtime ban among more than 2,000 staff is likely to see a return to short-notice cancellations like those when ScotRail drivers unofficially stopped volunteering for overtime in May as part of their own pay dispute.
ScotRail said it relied far less on RMT members doing overtime to keep services running than drivers and the Scottish Government firm does not expect to have to introduce a reduced timetable, as it did during the drivers’ dispute.
However, the RMT represents staff such as conductors, with the trains they operate unable to run if the overtime ban leads to a shortage and no suitably-trained managers are available to step in.
Such trains operate across most of the ScotRail network other than in and around Glasgow.
ScotRail said the number of cancellations might depend on sickness levels and other short-notice absences.
The RMT said its action would have a “massive impact”, with Sundays particularly affected as it was not part of the working week.
Other workers due to take part include train ticket examiners, station staff, cleaners and maintenance engineers known as fitters.
The RMT has rejected a series of offers since May, which have increased from an original 2.2 per cent to 5 per cent with other benefits and payments increased.
The union is seeking a 8.2 per cent rise.
Drivers' union Aslef agreed a 5 per cent deal with ScotRail in July.
RMT general secretary Mick Lynch has predicted that a resolution to the ScotRail dispute will be easier than one in the union’s separate pay and conditions dispute with English-based train operators, which has led to eight days of strikes across the British network.
He told the Commons transport committee on Wednesday: “We will get a solution with ScotRail in a more comfortable way than with the train operating companies that are governed by the [UK] Department for Transport.”
RMT Scottish organiser Mick Hogg said on Thursday: “We are disappointed ScotRail does not have the authority to make an improved offer despite offers above 5 per cent being made to refuse workers, teachers and now nurses.”
ScotRail head of customer operations Phil Campbell said: “We are really disappointed with this additional industrial action which will again impact on our customers following the strike action earlier in the week.
“We rely on staff working overtime as we recruit to fill vacancies, and unfortunately there will be some daily cancellations starting from Friday and throughout the period of the RMT’s ban.”
Scottish Conservatives transport spokesperson Graham Simpson said: “Our rail service is caught in the middle of a selfish dispute between the militant RMT union and incompetent SNP management, and ordinary passengers are suffering.”