Hundreds of abattoir workers in Anglesey and Flintshire will take industrial action over plans to impose 21 redundancies.
Dutch firm Vion owns the abattoir sites.
It has announced plans to cut almost 820 jobs across Britain – including in Suffolk, Yorkshire and South Lanarkshire.
Over 300 workers in the Unite union at Welsh Country Foods abattoir in Gaerwen and over 500 at Grampian Country Foods sites in Llangefni and Sandycroft will take part in national action to defend jobs.
The action will involve an overtime ban and implementing “work to rule”, but workers have narrowly voted against taking strike action at this stage.
Unite members voted by 60 percent to take industrial action, and 51 percent voted against taking strike action.