Around 50 Siptu members picketed outside at four Fás offices in Dublin for just over two hours this morning as part of industrial action against the Government's decentralisation programme for the State agency.
Last month, Siptu members at Fás voted overwhelmingly to take industrial action in opposition to the planned move to Birr, Co Offaly.
Today's pickets were held at the Fás head office on Dublin's Baggot Street as well as offices on Clyde Road, South Circular Road and Peter Street.
According to the union, only six of the 400 Fás head office staff have expressed their wish to move to Birr, Co Offaly, but that since it was linked to promotion, that number had risen to 28.
The strike comes after talks between representatives from Siptu and management of Fás at the Labour Relations Commission last night broke down.
"Workers are protesting against the management's plans to decentralise the agency to Birr, Co Offaly - without Union agreement and despite the fact that only a small minority of the 400 staff at FÁS have agreed to move," Siptu's Fás Branch Organiser Greg Ennis said.
"Ten hours of talks at the Labour Relations Commission failed to resolve the issue," he said adding, "This it is the first of a series of stoppages over decentralisation," Mr Ennis added.
Fás has said it is implementing Government policy.