The result improved the Ticos' record in tournament openers to 10 wins and two draws in 12 games, including four victories against Belize.
Before the visiting defense had an opportunity to get its bearings, Costa Rica came close to netting within the first minute. Forward Jairo Arrieta nailed a right-footed shot off the post of Woodrow Wilson's goal.
As the half wore on and the Ticos continued to apply pressure, Belize looked increasingly dangerous on the counter and created some half chances.
The opening 45 minutes, however, ended without the breakthrough the home crowd had hoped for, but the locals wouldn't have to wait long to celebrate a goal.
Ten minutes into the second half, after a series of rebounds, Arrieta found the ball at his feet in the box and smashed an unstoppable drive past Wilson into the upper left corner for his first career Copa Centroamericana goal.
The host failed to find the net a second time, instead making its lone strike stand, to take three points and the lead atop Group A after one round of play.
Despite three of its last five Copa Centroamericana outings having been decided by one goal or less, Belize remains winless in 21 all-time tournament games.
Costa Rica will next take the field on Sunday to face Guatemala, while Belize takes on Nicaragua the same day.