OCBC Bank and United Overseas Bank (UOB) customers can now make unlimited withdrawals from either bank's ATMs until the end of the year without incurring fees.
Previously, if an OCBC client used a UOB ATM, he would have to pay 30 cents each time after using up his allocation of two free withdrawals a month.
The same went for a UOB customer using an OCBC ATM. Other functions include being able to check account balance and transfer funds on another bank's ATM.
The system of two free cross- bank ATM cash withdrawals a month has been in place since 1988.
Fees that kicked in after the two free ATM uses are being waived until Dec 31. This means customers of either bank can use the other bank's ATM network as often as they want to - at no charge.
The banks want to raise awareness of the shared ATM network and the cross-bank cash withdrawals, fund transfers and balance inquiry services available.
The aim is to increase cross-ATM transactions by 10 per cent and to make cash withdrawals faster and more convenient.
Mr Dennis Tan, OCBC's head of consumer financial services Singapore, said: "Although this shared ATM network service has been in place for close to 30 years, we want more of our customers to be aware of this convenience."
There were more than five million cross-bank transactions by customers using the shared ATM network last year.
Such transactions have risen 30 per cent over the past 10 years, signalling potential customer demand, the banks noted in a joint statement.
Ms Jacquelyn Tan, UOB's head of personal financial services of Singapore, said: "There are three things customers expect when it comes to banking services: make it faster, simpler and more convenient.
"This partnership delivers on all three expectations as customers have more ATMs to choose from and do not have to worry about capping their usage to only two cross-bank ATM withdrawals per month."