Workers at computer giant Fujitsu will stage the first of six 24-hour strikes today in a row over pay, pensions and jobs.
Members of Unite will walk out ahead of further stoppages in the first few weeks of January, after voting in favour of industrial action.
The union said it will be the first national strike in the IT sector in the UK and follows a clash over a pay freeze, plans for up to 1,000 job losses and moves to close the final salary pension scheme to new entrants.
Unite national officer Peter Skyte said: "Our members are clearly angry with the way the company has treated them. Their pay has been frozen, compulsory redundancies are being pushed through and their pension scheme is under attack. All of this is happening at a time when the company is making substantial profits.
"It seems that the company are hiding behind the recession to attack the pay and conditions of their workforce.
"Our members would prefer not to strike, but feel strongly that Fujitsu is not listening to their genuine concerns and that enough is enough.
"We want the company to return to the negotiating table with a sensible offer acceptable to our membership."
Fujitsu employs around 11,000 people in the UK at sites including Derry.