Though far from easy, the Central American side posted a 2-1 victory over its Caribbean opponent, ensuring that it and the Mexicans would progress to the knockout stage.
Olivier Ayala put the Salvadorans ahead in the 24th minute, executing a neat back-heel inside the six-yard box after Melvin Alfaro's mishit shot found its way to the unmarked 19-year-old defender.
Just before half-time, Jose Peña nearly doubled the lead, but his attempt to chip Curacao goalkeeper Zeus de la Paz him from 30-yards out floated wide left.
Curacao needed at least a draw to avoid elimination, but miscommunication between de la Paz and Shuremy Felomina at the edge of the 18-yard box in the 65th minute allowed Romel Mejia to score easily into an empty net.
Down 2-0, with 14 minutes left in the game, Vidarrell Merencia made things interesting for Curacao with a brilliant individual effort to halve the deficit. The 18-year-old, who plays for ADO Den Haag in Holland, gained possession on the right 40 yards from goal, dribbled towards the Salvadoran penalty area and uncorked a curling shot with his left foot that snuck inside the far post.
El Salvador endured some nervous moments prior to the final whistle, especially in the 87th minute, when a Curacao free kick crashed off the post.
Mexico and the Cuscatlecos will face off Saturday for the top spot in the group. The Mexicans, who beat Curacao 3-0 on Tuesday, need only a draw to finish first.