According to Southern Rail, a flooded underpass between platforms one and two means passengers are not able to get to, or exit, trains going towards Brighton and London.
The problem was first reported at around 8pm yesterday (January 31) and appeared to have been cleared, but reemerged overnight.
Engineers are expected to clear the flooding at 8am, with Southern Rail hoping travel can resume as normal at 10am.
Trains heading west towards Littlehampton are unaffected.
Anybody travelling to Worthing station from the west is advised to get off at East Worthing.
Travellers wanting to get to Brighton from Worthing are advised to get the train to West Worthing station from platform three and get the train east from West Worthing.