Bananas are among the worlds’ most economically significant fruit crops, valued for their distinctive flavour and aroma, despite being highly susceptible to rapid postharvest physiological deterioration. Melatonin, a non-toxic bioactive compound, regulates several plant physiological processes and is widely studied in postharvest management. With this background, the study investigated the effect of different concentrations of melatonin on three banana varieties, namely Grand Naine (AAA), Poovan (AAB) and Ney Poovan (AB). The fruits were stored under ambient (AS) (27 ± 2°C) and cold storage (CS) (17°C) with 90–95% relative humidity. Melatonin treatment (1000 µM) effectively reduced weight loss, retained firmness and total soluble solids, reduced ethylene production, enhanced chlorophyll retention and delayed starch degradation. Grand Naine showed the most pronounced effects, followed by Ney Poovan and Poovan. Overall, 1000 µM melatonin was the most effective treatment for extending banana shelf life and maintaining quality under ambient and cold storage conditions.