Essential oil of Plectranthus amboinicus was studied for its chemical composition and larvicidal potential against the malarial vector mosquito Anopheles stephensi. Totally 26 compounds were identified by GC and GC-MS. The major chemical compounds were carvacrol (28.65%) followed by thymol (21.66%), α-humulene (9.67%), undecanal (8.29%), γ-terpinene (7.76%), ρ-cymene (6.46%), caryophyllene oxide (5.85%), α-terpineol (3.28%) and β-selinene (2.01%). The larvicidal assay was conducted to record the LC50 and LC90 values and the larval mortality was observed after 12 and 24 h of exposure period. The LC50 values of the oil were 33.54 (after 12 h) and 28.37 ppm (after 24 h). The LC90 values of the oil were 70.27 (after 12 h) and 59.38 ppm (after 24 h). The results of the present study showed that the essential oil of P. amboinicus is one of the inexpensive and eco-friendly sources of natural mosquito larvicidal agent to control/reduce the population of malarial vector mosquito.