Members of the Psychiatric Nurses Association will strike in February in their dispute over pay and staff shortages.
The Association's 6000 members will refuse to work overtime on January 31, or on February 5, 6 and 7.
Industrial action will be escalated to full strikes on February 12, 13, and 14.
95% of PNA members rejected government proposals to address recruitment and retention issues among nurses.
INMO members announced on Tuesday that they will strike on January 30, as well as February 5, 7, 12, 13 and 14 unless their pay demands are addressed.