Vulnerable adults with disabilities will be left without some services as SIPTU members at the National Advocacy Service down tools.
They're striking over pay and conditions and say the government has failed to implement Labour Court recommendations.
There are pickets outside National Advocacy offices countrywide, including Cork city.
SIPTU's says staff feel had to walk off the job:
"So they've been left with no choice but to take strike action, and it is going to have a very serious impact, we know, on people with disabilities, but feeling is amongst the workers that if they don't do this, people are leaving the organisation and there will be no organisation for vulnerable people into the future."
