Costa Rica Wrap: Arias fires Herediano to summit
Jorge Arias scored the game's only goal, sending Marvin Solano's men top with 12 points from five matches and relegating Alajuelense to third spot three points back.
Herediano also benefitted from Cartagines' slip up at Puntarenas, as the former league leaders lost 2-0 after conceding twice in the final 20 minutes.
Roberto Wong and Diego Brenes were the goalscorers for Puntarenas as they struck eight minutes apart to knock their opponents off top spot.
UCR also fell to defeat as their road trip to Carmelita saw them go down 2-1.
Ronney Mora struck late in each half to see Carmelita come from behind and take all three points, and back-to-back wins sees them into seventh - level on points with fifth-placed UCR.
Santos de Guapiles is sandwiched between those two sides, also on seven points, in sixth, after earning a 1-1 draw away to Belen Siglo XXI.
In other results, Limon accounted for Perez Zeledon 1-0, while Deportivo Saprissa smashed Uruguay 4-2 thanks to a double from Ariel Rodriguez, sending the winners into fourth place on eight points.