It is extremely important to identify an alternative capable of minimizing the effects of salt stress on plants. In this context, the objective of this study was to evaluate the physiology, growth, production, and post-harvest quality of mini watermelon as a function of irrigation water salinity and hydrogen peroxide. The experiment was conducted in pots adapted as drainage lysimeters under greenhouse conditions, using a randomized block design in a 5 × 4 factorial scheme, corresponding to five levels of electrical conductivity of irrigation water – ECw (0.3 – control, 1.0, 1.7, 2.4, and 3.1 dS m−1) and four concentrations of hydrogen peroxide – H2O2 (0, 20, 40, and 60 μM), with three replicates. The results obtained in the present study indicate that Sugar Baby mini watermelon is sensitive to saline stress, with its physiology, production, and fruit quality negatively affected by irrigation with water of electrical conductivity above 0.3 dS m−1. However, foliar application of hydrogen peroxide at a concentration of 20 µM partially reduces the harmful effects of saline stress, especially for plants irrigated with ECw of 0.3 dS m−1.