Having spent the 2012-13 season in Argentina's second tier before earning promotion to the Primera Division, Olimpo had started the 2013-14 campaign poorly with three losses and two draws but broke through for their maiden win on Sunday.
Martin Perez Guedes scored twice for Olimpo as the Bahia Blanca-based club triumphed over visiting Boca.
The hosts took the lead in the seventh minute when Boca's defence failed to effectively clear Paulo Rosales' cross and the ball was sent back into the penalty area, where Guedes finished from close range after a shot from one of his teammates was deflected into the right winger's path.
Striker Augustin Vuletich doubled Olimpo's lead with 20 minutes remaining when he got on the end of Damian Musto's flicked header from a corner to volley home at the back post.
Guedes scored the home side's third goal, getting his head to Ivan Furios' flick, following a free-kick from Rosales.
Osvaldo Miranda scored the only goal of the game in the 29th minute when Hernan Boyero touched Rodrigo Gomez's cross into the path of his striking partner to finish from close range.
In other results, Velez Sarsfield won 3-0 over Newell's Old Boys, Estudiantes drew 1-1 with Belgrano and Godoy Cruz defeated Colon 1-0.
