Two field experiments were done at a privet farm in Mansoura, Dakahlia Governorate, Egypt, during the two summer consecutive seasons of 2019 and 2020. The research objective of this work was to examine the influence of foliar application of nano-chitosan at different concentrations (0, 25, 50 and 100 ppm) under different phosphorus fertilizer level (0, 16, 32 and 48 kg P₂O₅/feddan) on hot pepper "cv. Hyffa" productivity. The influence of phosphorus fertilizer, nano-chitosan and their interaction treatments were determined on plant growth, yield components, some chemical constituents. Phosphorus fertilization at 48 kg P₂O₅/feddan significantly increased hot pepper growth (plant height, number of branches per plant and total plant dry weight), yield components parameters (fruit set %, fruit length, fruit diameter, fruit yield per plant and early yield and total yield per feddan) and chemical constituents (total chlorophyll, total soluble solids, vitamin C, total nitrogen%, total phosphorus % and potassium %) as well as capsaicin content in fruits compared to control and the lowest levels under study. In addition, increasing nano-chitosan concentrations gradually increased all measured parameters to reach the highest values with 100 ppm concentration as foliar spray compared to the other treatments under study. Generally, the results of this work demonstrated that foliar applications of 100 ppm nano-chitosan could help enhance hot pepper (Capsicum annuum, L.) growth and productivity as well as content of alkaloids (determined as capsaicin) when interacted with 48 kg P₂O₅/feddan under Dakahlia Governorate conditions.