As a global commodity, cotton plays a major role in the economic and social development of emerging economies and newly industrialized countries. Egyptian cotton occupies a unique and important place in the world market because of its high quality and long staple fiber. Unfortunately, the Egyptian cotton plant has been attacked by Spodoptera littoralis leading to huge economic losses. Excessive and uncontrolled use of chemical insecticides resulted in food contamination as well as environmental, agricultural, and aquatic pollution. Nanotechnology opened new avenues for manufacture of more environmentally safe pesticides. Photosensitizers can also contribute to produce cost-effective and ecofriendly pesticides, photopesticides. In this study, we prepared a hematoporphyrin-gold (HP-AuNPs) nanocomposite as a model for smart generation of photopesticides processing high photodynamic cytotoxic actions. The prepared Photopesticides was characterized by UV-VIS spectroscopy, FTIR, and transmission electron microscopy (TEM). The prepared composite exhibited no appreciable toxicity to S. littoralis without exposure to light. The prepared nanocomposite exerted high phototoxicity against the 2nd instar larvae of the Egyptian cotton leafworm in a concentration-dependent manner (LC50 = 0.9 ppm of gold). The performed biochemical analysis of the tested groups revealed that dipping of the second larval instar of S. littoralis in aqueous solution of (HP-AuNPs) nanocomposite (LC50) followed by light exposure (halogen lamb 500 W, 4h) resulted in a remarkable incitement of α- and β-esterase activities, alkaline phosphatase, total protein, total carbohydrate, acetyle choline esterase and mixed function oxidase activity.