Branches at Cregagh Road in Belfast, Ballyclare and Limavady will shut in May, while outlets in Larne, Holywood and Fortwilliam in Belfast will close the following month.
Staff employed at the branches will be relocated to other outlets or offered voluntary severance.
A dedicated helpline number will be provided for customer queries on the closures.
Last year, between October and December, five branches closed and staff were relocated. Over 40 branches shut in 2012 in the republic.
In a statement released on Wednesday, the bank said that customer account numbers, sort codes, or the existing operation of their accounts will not be affected.
Customers will be informed by letter that their accounts will be automatically transferred to the nearest First Trust branch.
Gerry McGinn, the bank's Managing Director, said the bank continues to retain a very strong network of branches throughout Northern Ireland.
"Regrettable as they are, the closures are part of an ongoing strategy to bring the Bank back to a sustainable operating model and will not involve compulsory redundancies.
"Like all retail businesses, we must constantly review our costs in order to move forward as a more streamlined and sustainable organization," he added.
Mr McGinn explained that the detailed review of the branch network considered "how customers are using our branches and how they're adapting to our continuing innovations in technology."
"It is never an easy decision to close branches and our focus is on minimising inconvenience to our customers and continuing to provide them with a professional, efficient banking service."