Otman Bakkal scored the only goal to keep Feyenoord's slim Eredivisie title hopes alive and knock opponents AZ Alkmaar out of the race for the championship.
Bakkal struck early in the second half, with the result moving Feyenoord up to second and six points being Ajax with two rounds remaining, although the Amsterdam club have a far superior goal difference.
AZ slip nine points behind the leaders and will now focus on ensuring a top-three finish and European football next season.
Sekou Cisse had the Rotterdam club's first chance after four minutes with a shot just wide of the post following Ruben Schaken's cross.
Brett Holman responded for AZ with a 25-yard drive which also fell wide, but Feyenoord soon began to assert their authority and Bakkal gave them hope of an opener when he raced into the area before pushing his shot past the post.
Ron Vlaar then put a header over the bar before the interval as AZ clung on.
The hosts picked up where they left off at the start of the second half and Bakkal's pass to Schaken was almost turned in from close range by the forward.
Schaken came even closer to scoring after 52 minutes with a powerful strike which clattered the crossbar.
However, Bakkal made amends two minutes later, running on to a pass from Vlaar before unleashing a shot from 22 yards which hit the inside of the right post before nestling into the net.
AZ played better after the goal, and home goalkeeper Erwin Mulder had to fist away a strike from distance from Adam Maher.
Mulder made another good save to turn away a shot from Holman which was heading towards the top left corner.
AZ then almost snatched an equaliser in stoppage time with Holman smashing a shot narrowly over the bar on the turn.