Buses will replace trains from Bicester North Station to Princes Risborough at the weekend due to signalling work.
Engineers will be installing new equipment as part of the Evergreen 3 project linking Oxford with London Marylebone via Bicester.
Trains from Banbury will terminate at Oxford for First Great Western services to London Paddington.
People are advised to check before they travel.
For more information, see the website chilternrailways.co.uk