This study investigated effects of ketamine on the development of Chrysomya Megacephala (Diptera: Calliphoridae) at three different temperatures. Larvae of the C. Megacephala were exposed to different concentrations of drugs and temperatures. The larval lengths, weights, and developmental durations of each stage were observed. This study demonstrated that ketamine, low temperature, and their synergistic action significantly suppressed the development of C. Megacephala (p < 0.001). The time that the larvae in all the treatments achieved the maximum length/weight was significantly delayed (p < 0.05), and that resulted in prolonged duration of larval and prepupal stages especially at low temperature. However, no linear correlations were discovered between ketamine concentration and growth rate of larval length/weight.