Workers at 70 Tesco stores around the country are set to strike
Mandate says that pickets will be placed on outlets from 7am on Monday May 16.
The trade union claims its as a result of the company implementing pay cuts and changes to conditions of employment for up to 300 of their staff.
Mandate general secretary John Douglas said that Tesco are not treating some employees fairly.
"The workers in Tesco decided that they would vote for industrial action," he said.
"We have a mandate for industrial action. We've served notice on the company that if they attack our members on the 16th of May, that our members will be on strike right across this country."
Tesco has opened a voluntary redundancy scheme and has deferred reductions in pay and conditions until May 16.
The company has said that it remains open to constructive discussions in the Workplace Relations Commission.