Velez clinched their ninth league title with a match to spare, taking 38 points from 18 matches for an unassailable five-point lead over second-placed Lanus, who lost 1-0 at River Plate.
It was coach Ricardo Gareca's third championship with Velez in three and a half years.
"Chucky" Ferreyra put Velez in front with a header and took his championship tally to 11 with a brilliant second goal, curling the ball left-footed inside the far post from striker partner Lucas Pratto's low right cross.
"I'd like to thank Gareca for the faith he showed in me," the 21-year-old Ferreyra told reporters.
Right back and captain Fabian Cubero, a veteran of all three championship victories under the same coach, added: "[Gareca] knows how much we love him."
River, watched from the heaving Monumental stands by new coach Ramon Diaz, who takes charge on Monday, scored in the 76th minute when Uruguayan striker Rodrigo Mora headed home midfielder Leonardo Ponzio's free-kick from the right.
"It was a very good farewell for [departed coach Matias Almeyda] and a welcome to his successor," Ponzio told reporters. Almeyda quit during the week and reserve team coach Gustavo Zapata took charge for Sunday's match.
Coach Juan Antonio Pizzi's San Lorenzo notched a fourth win in five matches, coming from a goal down to beat Independiente 2-1 at home to keep the Red Devils mired in relegation trouble.
