ANZ says an outage prevented some customers from accessing its app or logging into its internet banking website for several hours.
The outage began early Tuesday afternoon and lasted for about two hours before access began coming back online.
The bank tweeted that it was "a technology issue relating to a third party vendor".
ANZ said its ATMs, phone banking, the ANZ Plus app, EFTPOS facilities, Apple Pay and Google Pay were not affected the outage.
Its rival Commonwealth Bank suffered a similar major outage in March that prevented customers from accessing online services.
