Bus drivers will refuse to collect or drop off passengers at Busaras after dark due to an increase in attacks and anti-social behaviour.
The drivers will take the action from next Monday unless Bus Eireann agrees to provide more security at the station.
NBRU General Secretary Dermot O'Leary said there has been a noticeable increase in attacks over the last six months, with one driver recently suffering a very serious assault.
Speaking on Newstalk Breakfast this morning, he said: "The driver involved was loading a passenger onto the 126 Newbridge route and the individual who was getting on didn't have the appropriate travel documentation.
"They were challenged and they attacked the driver and assaulted him pretty seriously."
Drivers have told the union chief that there is a severe lack of security guards at the country's busiest bus station.
He said: "Busaras, at this point in time as we understand from our members, you might get one security or two sometimes around that big depot.
"We've been calling for some time as you know for a garda public transport division to try and help and police public transport and whilst different types of resources would be needed for buses as opposed to trains, that campaign goes on but at Busaras it's up to the company at this stage to provide adequate security."
He added: "It's not industrial action in the normal way...this is people taking their own safety very seriously and that of their passengers very seriously and they're not going to take that chance any more."
A Bus Eireann spokeswoman confirmed they have been in contact with the NBRU in relation to ongoing issues of anti-social behaviour.
She added: "The safety and security of customers and staff is of paramount importance to Bus Éireann.
"Busaras has extensive CCTV cameras throughout the bus station as well as 24 hour security personnel on site and we will continue to work and engage with the Trade Unions on this matter."
