Eremomastax polysperma is a widely used medicinal plant among the Efik/Ibibio communities in southeastern Nigeria for treating various ailments through traditional medicine. This study investigates the seasonal variation in phytochemical content, antioxidant levels, and physicochemical properties of the leaf and its aqueous extract to validate its ethnomedicinal use and determine the season of peak maturity based on chemical concentrations. Standard analytical methods were employed. Results indicated significant seasonal differences in phytochemical levels: alkaloids, flavonoids, and saponins were higher in the wet season, while tannins and hydrogen cyanide (HCN) were elevated in the dry season. Vitamin A content peaked during the dry season, whereas vitamin C was more abundant in the wet season. Physicochemical parameters also varied: temperature, conductivity, suspended solids, dissolved oxygen, total hardness, sulphate, and chloride levels were higher in the dry season, while pH, total dissolved solids, titratable acidity and alkalinity, biochemical oxygen demand (BOD), and nitrate were more prominent in the wet season. These findings confirm that seasonal changes significantly affect the chemical composition of E. polysperma, and the plant can be harvested in either season depending on the desired therapeutic effect