AIB has said all of its services are now operating as normal, following technical issues earlier on Thursday.
The State-owned lender had advised customers to use internet banking as an alternative to mobile services until the technical problems were resolved.
Customers’ ability to withdraw cash from ATMs and make purchases in store and online with their AIB cards was not affected.
AIB, which has more than one million active users of its online services, apologised for the service outage and said its IT staff were working to resolve the problem as quickly as possible.
Earlier in the day the bank said it was experiencing some technical issues online, in branches and on the phone, that were affecting transactions.
Customers of the bank also had problems using internet services and tablet banking for a period of hours late last month.
AIB is not the only bank to have had experienced technical issues of late. Bank of Ireland customers also experienced difficulties in late June due to a technical glitch that temporarily affected debit card users.