Eagles boss Peter Taylor has been keen on Fonte, 22, for some time, and he now appears to have sealed a loan deal with the option of a permanent move next summer.
The Portuguese youngster has flown over to England to put the finishing touches to the deal and to undergo a medical.
"After some really positive news I'm very hopeful we've now tied up the Fonte deal," Taylor told the Croydon Advertiser.
"We're confident everything's been agreed and he'll be flying over for a chat and a medical.
"I'm very excited about this young boy because I think he's a good centre-half and a good footballer, so I'm looking forward to working with him.
"We've hopefully got him for 12 months, with a small loan fee payable to Benfica. Then there'll be a bigger fee to pay after a year, if he likes us and we like him, so we've got the option of making it permanent."