Growing tomatoes is affected by a wide range of environmental conditions, including salt stress. A factorial experiment was conducted to evaluate the efficacy of melatonin and boron in mitigating the adverse effects caused by salinity stress on tomato (Solanum lycopersicum L.) physiology and fruit quality. The experiment consisted of applying three levels of melatonin (0, 200, and 400 mg L^-1) and three levels of boron (0, 5, and 10 mg L^-1) to tomato plants. The results demonstrated that melatonin and boron mitigated several damaging effects of salt stress, including a reduction in chlorophyll content, antioxidant activity, lycopene concentration, and reduced sugar levels. Exogenous application of melatonin and boron improved all traits negatively impacted by salt stress. Melatonin at 400 mg L^-¹ markedly enhanced chlorophyll synthesis, antioxidant enzyme activity, and elevated lycopene and sugar contents. Similarly, boron at 5 mg L^-¹ has been shown to promote chlorophyll stability, sugar transport, and enhanced nutrient uptake. Across all salinity levels, the combined application of melatonin and boron produced superior responses compared with individual treatments. The optimal treatment was S0M2B1 (no salt stress, melatonin 400 mg L⁻¹, boron 5 mg L⁻¹), which showed a significant improvement in the overall fruit quality and physiological performance of the tomato plants over all other treatments. The results of this study indicate that through the coordinated use of melatonin and boron, it is possible to effectively mitigate the adverse effects of environmental salinity on tomato plant growth, yield, and quality.