Darlington Crown Street Library is to close with a new service opening at the Dolphin Centre.
Despite a series of protests against the proposals, Labour councillors voted unanimously in favour of the move.
The new Dophin Centre library will have extended opening hours, opening 7 days a week, including a Sunday and two late night openings.
The number of staff will be reduced from up to six staff on duty down to four staff.
A move to a self-service check-out machine is expected to free up staff to focus more on assisting users with core library queries.
Crown Street Library was gifted to the people of Darlington by railway pioneer Edward Pease.