Deutsche Bank will close about 250 of 550 Postbank branches over the next three years as it works to turn the unit into a "mobile-first" provider.
Of the remaining 300 branches, 200 will continue to offer both banking and postal services, with the remaining 100 focused exclusively on banking, according to the FT.
Postbank has proved a challenging business for Deutsche Bank since its acquisition during the 2008 financial crisis.
Deutsche tried to sell off the business a decade later but abandoned the plan and embarked on a huge and troubled IT integration project that was finally completed this year.
However, glitches persisted and last month German watchdog Bafin reprimanded the bank for faulty operations and disruption of services in Postbank, appointing a supervisor to oversee customer service.