The spread of the red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera:Curculionidae), is a serious challenge at present due to the serious damage it causes to the date palm tree. This study investigated the ethanolic extract of Punica granatum peel and found that it leads to significant mortalities in both the larvae and adult stages of R. ferrugineus after exposure to four concentrations (4.7, 9.3, 18.7, and 37.4 mg/mL). The larvicidal effect reached 48% at day 6 for the 37.4 mg/mL concentration, and adults exhibited full mortality at the same concentration. In addition, the cuticle of treated larvae was investigated histopathologically, and corrugation and a thinning surface were found. Scanning electron microscopy revealed a strong uptake and aggregation of the extract on the glandular pores of the back wings of adults. The impact of P. granatum peel extract on the total protein content of the hemolymph of R. ferrugineus larvae was also studied. Compared to controls, larvae had 12 different bands before treatment, 4, 3 and 2 bands in common after treatment at concentrations 4.7, 9.3, and 37.4 mg/mL, respectively. These results suggest that P. granatum peel extract is a promising alternative to chemical pesticides and can be used as a biopesticide against larvae and adult red palm weevil.