The bank says services will be merged with other nearby locations.
The vast majority of the amalgamations are happening in Dublin and Cork - in urban and suburban locations.
The Dublin branches to close include Donnybrook, Sutton, Sandyford Skerries, O' Connell Street and Dalkey.
In Cork, the Little Island, Douglas Court and Ballyphehane branches are among those impacted.
Their services will be amalgamated with nearby branches.
AIB says the process will get underway in September and should be complete by December.
The bank says it's made the decision to close the 15 locations due to declining branch visits.
Customers do not need to take any action - and all affected customers will be provided with details from their bank.