<p>Horticultural crops play a significant role in meeting global food demand and nutritional security. It includes a wide variety of ornamental plants, fruits and vegetables. However, horticultural crops are vulnerable to various abiotic stresses such as drought, salinity, extreme temperatures and heavy metal toxicity. These stresses activate the production of Reactive Oxygen Species (ROS), which interrupt the crop’s physiological functions, development and yield. In the search for environmentally friendly stress management practices, melatonin, a pleiotropic molecule first discovered in animals and later in plants, has received significant attention for its role in stress mitigation. In abiotic stress condition, melatonin regulates ion homeostasis, maintains osmotic balance, stabilizes cellular membranes and improves the photosynthetic system. Moreover, melatonin interacts with various phytohormones, including auxins, abscisic acid (ABA), gibberellins, cytokinins, ethylene, jasmonic acid (JA), and salicylic acid (SA), by modifying plant responses to stress through hormonal crosstalk. Melatonin controls stress-responsive genes and transcription factors by enhancing the plant’s development at the molecular level. This review elaborates on melatonin’s biosynthesis and its roles in mitigating drought, salinity, heat, cold, and heavy metal stress in horticultural crops. It also discusses future research prospects, which include genetic engineering of melatonin biosynthetic genes, nano-formulations for targeted delivery, and multi-omics approaches to resolve regulatory networks. Future research should focus on crop-specific applications, field validation, and biotechnological innovations to study melatonin’s potential in climate-resilient horticulture.</p>