Non-Bank of Ireland customers who took out cash at Bank of Ireland ATMs on Tuesday experienced a double debit on their account.
The bank says the issue that caused the error has now been resolved.
The bank added it is working to rectify the duplication and apologised for the inconvenience.
Responding to social media users who highlighted the error, Bank of Ireland stated: "A number of non-Bank of Ireland customers who made cash withdrawal at BOI ATMs experienced a duplicate debit on their account.
"This has now been resolved. We're working to rectify the duplication for those impacted so accounts are corrected ASAP.
"We apologise for the inconvenience."
Last month, BOI imposed a number of restrictions on some customers' debit cards over fears they have been compromised by fraudsters.
BOI said there was heightened precautionary activity due to the increase in third-party data breaches.