"Whilst we cannot disclose dates at this stage, we can confirm that more than 25,000 union members will soon be embarking upon a protected strike," Saccawu said in a statement.
Describing the wage dispute as "deliberately protracted", it said preparations for the strike were underway.
Saccawu claimed the company was trying to "frog-march" it into a multi-year agreement and had made an offer which amounted to an "insult".
Saccawu members had mandated union leaders to co-ordinate a nationwide strike.
"Members have also mandated the union leadership to mobilise other civil society formations for an aggressive consumer boycott once members embark upon a protected strike," it said.
The union alleged that Pick n Pay management had "unilaterally and unjustifiably" terminated a job security and job flexibility agreement, causing serious tensions on the shop floor.
Management had also allegedly withdrawn the company's sponsorship of an annual shopstewards' council.
This usually provided management with a platform to share its strategic vision and future plans with shop floor leadership.
Saccawu accused the retailer's senior management of being "hell-bent" on petty issues instead of focusing on the strategic challenges facing the company.
"Members are now fed-up as they have to endure hardships on the shop floor and an uncertain future due to lack of strategic leadership from senior management," Saccawu said.
It said workers had been due increases in March. Those who fell outside the bargaining unit received their increases in July.
Saccawu alleged that Pick n Pay had been training "scabs" since mid-August.
Pick n Pay could not comment immediately.
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