Watermelon is a widely cultivated cucurbitaceous crop with economic and dietary significance. The plant's ability to reproduce effectively relies on the harmonious growth and maturation of both its male and female flowers. At the farm level, determining the exact amount of ethylene required to regulate the development and sexual expression of individual floral buds remains uncertain, despite the known influence of exogenously applied ethylene on these processes. The goal of the research was to explore how the ethephon doses influence vegetative characteristics, sex expression, and watermelon yield. The experiment, employing a one-factorial Randomized Complete Block Design (RCBD) comprising five treatments and four replications, was conducted in a farmer's field in Buttabari, Jhapa. Using R-stat software, the data were analyzed at a 5% level of significance. Treatment consisted of Ethephon with four doses namely; 100ppm, 200ppm, 300ppm, 400ppm, and a control. Ethephon application was done twice, once at the two true-leaf stages and another at four true-leaf stages. The study revealed that plant height decreased with ethephon compared to the control, reaching a minimum of 280.1 cm at 400 ppm and a maximum of 307.1 cm in the control. Additionally, the highest branch numbers were observed with ethephon at 200 ppm. The plot treated with 200ppm ethephon was found to be more effective than alternative doses at increasing the total number of female flowers, bearing 15.25 female flowers per plant. Control (166.50 per plant) and 400 ppm (150.00 per plant) had the highest and lowest male flower counts per plant, respectively. A maximum yield of 25.12 t/ha and a minimum yield of 19.1 t/ha were determined at 200 ppm and control, respectively. Hence, farmers are found to benefit from ethephon doses of 200 ppm.