Resumo. Due to the ability to locate the host plant over long distances, and the direct and indirect damage that are caused, Rhynchophorus palmarum L. (Coleoptera: Curculionidae) is considered a key pest of coconut crop. Therefore, the objective of this research was to evaluate the efficiency by contact of the insecticide thiamethoxam on adults of R. palmarum, determining the lethal concentrations (LC50 and LC90), under laboratory conditions. One mL of insecticide solution was applied to the insect body at concentrations of 1 ppm, 2 ppm, 3 ppm, 4 ppm and 5 ppm. Insect mortality in the treatments was evaluated after five days. The comparison of means was performed by the Tukey test at 5% significance. For determining the lethal concentrations of 50 and 90%, Probit analysis was performed. The LC50 (2.16 ppm) and LC90 (4.23 ppm) remained within the confidence interval. The concentration of 5 ppm caused 100% mortality, evidencing the efficiency of the insecticide by contact, demonstrating a promising alternative in controlling this pest.