Stefan Sykes is treasurer of St Paul's Centre Worthing Community Project Ltd, the charity which owns the building in Chapel Road.
He said that the café would be closing, and ten part time members of staff had been given notice.
He said: "The café has been loss-making for a while. We have tried cost cutting and different methods of keeping it open, but we have had to decide that the end has come for it."
But the building itself would remain open during the day, and the evening use of the iconic building as a venue for entertainments, events and weddings would be unaffected.
The café had served food and drinks from 8.30am to 4.30pm.
The space is also used by many groups during the day, and for meditation and mental health drop in sessions.
Mr Sykes said a team of volunteers 'had been stepping up very dutifully' to make sure the space remained open for them to use.
Provisional supplies of tea and coffee may still be provided for these events, he said.
The charity runs the trading company which operated the café and evening events side of the business.
Mr Sykes said the charity was looking for new operators to run both the day and evening trade, so they could focus on looking after the building.
He said they had received a lot of interest so far. The deadline for this was the end of May, he said, in the hope that the café could be reopened in June.
The charity was preparing a statement that it would be publishing online, Mr Sykes said.