Operator Stagecoach will be making the changes as part of county-wide improvements.
The changes have been made possible after East Sussex County Council made a successful bid to the UK Government to fund the Bus Improvement Plan.
Improvements to the 54 service, which operates between Uckfield and Eastbourne via Halland, East Hoathly and Hailsham, sees new extra evening services running from Monday to Saturday. Buses will also run on Sundays on this route for the first time.
The changes will be introduced from Sunday 23 July.