Red Palm Weevil (RPW), Rhynchophorus ferrugineus is widely regarded as the most serious pest of the date palm in worldwide, causing massive losses in palm crop and related industries. To prevent re-infestation, a promising chemical injection for effective control treatment at particularly high invested levels is required. Five different concentrations solution of formaldehyde in water were used to investigate the formaldehyde- RPW response. Results revealed that the concentration of 16% exhibited a remarkable effect on newly hatching and 2nd instar larvae of R. ferrugineus among all concentrations after 10 days exposure to poisoned medium. Data showed that there was significant increase in larval mortality by increasing the duration of exposure to formaldehyde. Data revealed that formaldehyde is potent against the larvae, thus, it could break down the life - cycle of R. ferrugineus and might be involved in the control programs of R. ferrugineus as a protective or curative material. In terms of LC50, the toxicity of formaldehyde on newly hatched larvae was the most effective. The time needed to cause mortality was decreased with increasing the concentration of the formaldehyde. Also, exposure of RPW to ascending concentrations of formaldehyde had significant effect between tested concentrations when applied on 4th instar larvae. The total lipids and total carbohydrates content decreased in all concentration treatments, while, no or slight decrease occurred in total protein, compared with those recorded in the control.