The purpose of the present study was to evaluate the effect of vernalization and GA3 on seed yield and reproductive quality of summer onion. There were three vernalization treatments viz., no vernalization (control), vernalization at 5°C for 14 days and vernalization at 10°C for 14 days and four GA3 treatment viz., 0, 50, 100 and 150 ppm. The two-factor experiment was conducted in the Randomized Complete Block Design (RCBD) with three replications. Combination between vernalization and GA3 was significant on the parameters such as plant height, number of leaves plant-1, the highest number of flowering stalk, number of umbels plant-1, number of bud umbel-1, percent flowering at 45 and 60 DAP, number of seeds umbel-1, weight of seeds umbel-1, weight of seeds plant-1, weight of seeds plot-1, 1000 seed weight, seed yield, number of fruits umbel-1, percent of fruit set umbel-1and percent germination. Combined effect of vernalization & GA3 was considered the highest seed yield (280.42 kgha-1) was obtained from vernalization at 5°C for 14 days with 100 ppm GA3. The lowest values of all the parameters were recorded in the control treatment. No limitation is found in the present experiment. Combined use of proper vernalization of mother bulb and suitable concentration of gibberellic acid can be one possible way to expand onion production during the summer.