Velez, who fought back from Alexis Castro's early strike for the side from Mendoza, snatched the "Inicial" championship lead that Newell's Old Boys had held for seven weeks.
Newell's dropped to second, a point behind Velez after being held 0-0 at their Marcelo Bielsa stadium in Rosario by Quilmes, whose goalkeeper Emanuel Tripodi made a string of fine saves.
Belgrano, two points further back, remained third after a 0-0 draw at home to Argentinos Juniors in Cordoba.
"Chucky" Ferreyra, who scored a hat-trick in Velez's 5-1 rout of title-holders Arsenal last weekend, equalised midway through the first half.
Defender Leonardo Sigali's weak back header left goalkeeper Nelson Ibanez stranded and Ferreyra reached the ball first, rounded him and slotted it into the empty net.
Ferreyra scored the winner in the 74th minute when his header from left back Emiliano Papa's cross was blocked and he rammed home the rebound for his seventh goal of the championship and Velez's fourth successive win.
Newell's coach Gerardo Martino's unbeaten side, who have lost their edge with three draws in their last four matches, said his side were influenced by their fans' anxiety for a victory that would keep them top.
"We were too hurried ... We didn't have cool heads to get the result that would have reflected our domination," he told reporters after Newell's enjoyed the lion's share of possession.
Lanus, who are in fourth place, can pull level with Belgrano if they beat Tigre at home on Sunday when Racing Club and Boca Juniors, a point further back, meet Arsenal and Colon respectively.