Excess salts in water used for irrigation in the semiarid region cause losses in growth and yield of cucurbits, such as watermelon. However, the choice of salinity-tolerant varieties can reduce the impact of stress on crop yield. Thus, the objective of this study was to evaluate the tolerance of watermelon varieties to irrigation water salinity during initial development. The experiment was conducted in a protected environment located at the Federal Rural University of the Semi-arid Region, Mossor & oacute;, RN, Brazil, in a randomized block experimental design in a 7 x 3 factorial scheme with four replicates, consisting of seven cultivars (Rochedo F1, Crimson Select, Charleston Gray, Fairfax, Crimson Sweet, Sugar Baby, Preciosa) and three irrigation water salinity levels (0.5, 4.5, and 9.0 dS m(-1)). Increasing irrigation water salinity reduced emergence, growth, and dry mass accumulation in seedlings. There was a tendency for photosynthetic pigments of watermelon seedlings to increase with increasing salts in the irrigation water, indicating that the time of exposure to salt stress was not sufficient to significantly reduce the levels of chlorophyll a, chlorophyll b and total chlorophyll. The Rochedo F1, Crimson Select and Fairfax varieties showed greater tolerance to salinity, while Sugar Baby and Preciosa were classified as moderately sensitive to electrical conductivity levels of 4.5 and 9.0 dS m(-1) in the irrigation water.