Some 1,800 Wilko workers have agreed to walk out in protest over a "brutal" new weekend rota system.
GMB Union said members will go on strike at the chain's two distribution centres at Worksop, Nottinghamshire, and Magor, Monmouthshire.
Nicola Savage, from the union, said some workers were now working every weekend when previously it had been about one in three.
One said working more weekends had made her "feel like a zombie".
Wilko said the new requirements were "within existing contracts".
There is no set date for the strike, which will see 600 walk out at the Magor site along with 1,200 in Worksop. The union said the move would "cripple" deliveries.
'I feel like quitting'
One worker, who wanted to remain anonymous, said she has worked all but two Saturdays since March.
She said it was getting in the way of seeing her husband, grandchildren and using her caravan, as she does not get two days off together.
"I feel like a zombie most of the time," she added. "I felt like quitting at one point but why should I have to give up my job after almost two decades?
"I've never gone on strike before but I will now. Something needs to be done, they have to listen to us."
Ms Savage said the values of the Wilkinson family, which owns the firm, did not extend to its employees.
She added: "Wilko prides itself on being a family-run company but they're imposing contracts that will force staff to work on the weekends, splitting up family time, without the agreement of their employees.
"The numbers show how strongly people feel about this."
A spokesman for Wilko said the firm shared workers' frustrations and is trying to reduce the number of weekends staff will work by recruiting more people.
He said it would also give 250 team members an additional weekend off, but the union said this had not yet made an impact.
The spokesman added: "The reality is that our customers expect to shop with us seven days a week and we must respond to meet our customers' needs.
"There are robust plans in place to ensure customers can continue to shop with us if any action occurs."