Mango (Mangifera indicaL.) is one of the most popular tropical fruits grown in Egypt and several other countries, making it a potential export commodity. Excessive deterioration after harvest requires various treatments to maintain fruit quality. We evaluated the treatments effects of melatonin (MT) as an anti-ethylene agent and tragacanth gum (TRG) as an edible coating individually and together (MT–TRG) before storing mangoes at 12 °C for 32 days under 85–90% relative humidity. Compared with control, all treatments were significantly effective in preserving fruit quality. Fruits treated with MT–TRG showed significantly lower decay values, respiration rates, ethylene production, and weight loss than untreated fruits. MT–TRG treatment significantly enhanced fruit quality, thereby maintaining fruit appearance, flesh color, firmness, total soluble solids and phenolic contents, and pectin methyl esterase, polyphenol oxidase, and peroxidase activities during the storage period. We propose 200 µM MT + 1% TRG as a safe postharvest treatment to reduce the deterioration of mangoes and maintain fruit quality.