Store and maintenance union members at six hospitals in Canterbury will begin a 24-hour strike on Thursday, after pay negotiations broke down.
The Engineers, Printers & Manufacturers Union said their pay is well below that of other employees.
Union organiser Ron Angel said 47 members want a pay rise of five percent, but Canterbury District Health Board has offered only 0.85 percent.
Mr Angel said that while the members are not frontline staff, they are crucial to the running of hospitals.
The strike is set to run from from 6am on Thursday until 6am on Friday.