The increasing use of fish in scientific research underscores the need for effective anesthetics to facilitate handling and transport. Eugenol is a promising alternative, yet its effects on Cnesterodon decemmaculatus larvae remain poorly understood. This study evaluated the impact of different eugenol concentrations on anesthesia induction and recovery time. A randomized controlled trial was conducted with 101 larvae housed in a 10-liter aquarium under controlled conditions. The experiment included two replicates. The larvae were divided into five groups: four exposed to eugenol (50, 25, 12.5, and 6 mgL⁻¹) and a control group exposed to ethanol (10 mgL⁻¹). Induction was assessed based on the loss of tail response, while recovery was determined by the resumption of normal swimming. Total length (TL) was measured, and body mass (BM) was calculated.