Growth attributes, yield and essential oil (EO) of lemongrass plant (Cymbopogon citratus (DC.) Stapf) in addition to some water relations and the economic return were assessed in response to the mutual effect of coefficients of cumulative pan evaporation (CPE) as a practical basis of irrigation scheduling at four levels (1.00, 0.85, 0.70 and 0.55 CPE) and foliar spraying with chitosan as antitranspirant compound (0, 50, 100 and 150 ppm). For this purpose, field study was implemented under sandy soil conditions during consecutive seasons of 2018 and 2019. Results exhibited that fresh and dry biomass per plant consequently, the herbage and dry yield per fed were enriched by irrigation scheduling at 1.00 and 0.85 CPE. However, irrigation scheduling at 0.70 and 0.55 CPE reduced all studied growth, yield attributes, oil yield and transpiration rate. EO yield per plant and per fed besides the oil main components were significantly enhanced by 1.00 or 0.85 CPE interacted with chitosan spraying at all levels in both harvests for the experimental seasons. The interaction between irrigation scheduling at 0.85 CPE and foliar spraying with 100 or 150 ppm chitosan significantly increased yield, oil productivity, and bioactive constituents particularly citral %. The premier productivity of irrigation water was recorded at 0.85 CPE compared with the other irrigation treatments. Hence, the optimum water requirement of 0.85 CPE interacted with foliar spraying of chitosan at 100 ppm as antitranspirant compound improved lemongrass yield, EO, economic return, water return and the productivity of irrigation water under water deficit conditions.