Caseworkers protesting what they say is chronic understaffing will gather outside an inner-Sydney community services centre on Wednesday.
The action comes after the state's child protection services were recently labelled ineffective and unsustainable by an auditor-general's report into the effectiveness of the Department of Communities and Justice.
A lack of staff in the sector has led to caseworkers seeing only one in four children reported to be at risk of serious harm.
That number is as low as 15 per cent in some parts of NSW.
The children who do get attention are at most serious risk and will likely be separated from their family, as staff shortages mean caseworkers aren't able to intervene early.
One in 10 caseworker positions are vacant, and the vacancy rate on any given day can rise above one in five.
One in two will quit within their first two years of employment and the remaining caseworkers report chronic burnout from picking up the extra workload.
Public Services Association general secretary Stewart Little called on the government to intervene.
"Child protection workers are now concerned that by exposing vulnerable children to a broken system, they may suffer even more harm," he said.
"The current NSW government didn't create this mess but it's up to them to fix it."
The association is calling on the government to recruit another 500 caseworkers, give caseworkers a pay rise and de-privatise foster care
Skeleton staff will stay at work during the strike to handle urgent cases, Mr Little said.