The Napo union will be staging a picket outside the probation offices at Sring Hall Lane, Halifax.
Nao has over 30 members in Halifax and more than 300 across West Yorkshire.
It is the biggest trade union for probation and family court staff and it’s only its fourth strike in 106 years.
Members voted to strike against the Secretary of State’s plans to privatise 70 per cent of the Probation Service.
They will walk out at noon for 24 hours and operate a Halifax picket from noon to 2 pm tomorrow.