His deal had been due to expire in 2017, but will now run for another 12 months.
"Eljero in his first year as Feyenoord been decisive for the team," technical director Martin van Geel said in a statement on the club's website.
"His contribution has been of great value to us and we are therefore very pleased that we were able to tie him down to Feyenoord."
Elia helped Feyenoord – who have already renewed deals for Kenneth Vermeer, Karim El Ahmadi, Tonny Vilhena and Dirk Kuyt – to a third-placed finish in 2015-16, scoring eight goals.
Giovanni van Bronckhorst's side also lifted the KNVB Cup, ensuring a spot in the Europa League.