Some services will now be offered at post offices instead.
Customers of 88 Bank of Ireland branches are using its local services for the last time today.
The closures were announced last March as part of the banks downsizing plan and shift towards an online service.
Some of the banks services, such as cash withdrawals and lodgments, will now be available through the post office network instead.
Both Bank of Ireland and An Post have confirmed the services are now in operation to facilitate transfer of funds.
A spokesperson for Bank of Ireland said:
"We know changes like this can cause concern for some customers.
We have ensured that the An Post partnership is up and running before any branches close, and we have communicated fully with all our customers about every option available to them online, in a nearby BOI branch or at a local post office."
