The Financial Services Union (FSU) and Permanent TSB have agreed union recognition and collective bargaining for managers in the bank.
Hundreds of Ulster Bank staff recently transferred to PTSB, which has increased FSU membership at the lender.
The union said the agreement will allow its manager members to collectively negotiate their pay and working terms and conditions with their employer.
"The banking landscape is changing, and it is vital the contribution and voice of staff is heard in ensuring that jobs and services for customers are safe and secure," said Gareth Murphy, Head of Industrial Relations and Campaigns with the FSU.
"This agreement sends a positive signal about the way PTSB wants to manage the industrial relations culture in the bank and is the start of a new relationship between the bank and the FSU," Mr Murphy said.
"This is part of our ongoing work to strengthen and expand collective bargaining," he added.
