Commercial Bank says the Ward Place branch will be open six days of the week.
Officials say there is a growing demand for more banking hours.
"In Colombo there is always a need to have additional hours so that customers can walk in after rush hours to do their banking, Commercial Bank’s managing director, Amitha Gooneratne said.
"Saturday is another convenient day for people to come and do their banking, so there is certainly a demand for that."
Commercial Bank already has around five of its branches in the vicinity of the new branch. It also has branches that are open 365 days.
Its latest branch would have two automated teller machines (ATMs).
The bank is planning to run the ATM as kiosks that offer multiple banking services.
"We will be trying to work on a kiosk basis where people can not only do ATM withdrawals, but also do internet ba