It follows failed mediation on May 8, when Idea Services negotiators walked out of union talks with no resolution in sight.
Up to 50 Dunedin staff, who are Etu union members, will walk off the job between 3.30pm and 4.40pm.
Members have agreed to return to mediation before the end of May, but Etu industry co-ordinator Alastair Duncan said it was unclear if Idea Services negotiators would turn up.
He said further strike notices had been issued for a fourth one-hour strike on May 31.
About 40 Idea Services staff picketed outside their office in King Edward St, Dunedin, early last month, and were among about 3000 nationwide.
Staff say they are fed up with chronic understaffing, which has left them feeling overworked and undervalued. They said they were tired of working long hours, including weekends, and wanted better pay to compensate for time away from their families.
There is also concern about plans to move support staff from house to house, to create more flexibility.
Staff said their clients were not coping with the constant changes in their carers, and it was resulting in staff being verbally and physically abused by their clients.
Idea Services provides support to about 4000 people with intellectual disabilities.
