NIPSA members working at the Ulster Folk and Transport Museums in Cultra, are set to take strike action on St Patrick's Day.
The strike action comes days after National Museums Northern Ireland announced a £50 million investment in the Co Down site and what the union have described as an "insulting" pay offer they have received, which has angered them so greatly they demanded to be part of the targeted NIPSA action.
NIPSA official Ryan Wilson said that staff have had enough of being paid poorly.