Resumo. The Cryptostegia madagascariensis Bojer ex Decne. species was introduced in Brazil with ornamental purposes, but currently, it is invasive in the Caatinga biome. Despite its high level of occupancy of altered areas of Caatinga, there is lack of information about this species, particularly in relation to the capacity of its seeds to germinate in adverse conditions. The objective of this study was to evaluate seed germination and the initial seedling growth of Cryptostegia madagascariensis in function of salinity at different temperatures. The experiment was conducted following a completely randomized design, with treatments arranged in a 6 x 3 factorial design with six salinity levels promoted by sodium chloride (NaCl): 0.0 (control); 2.0; 4.0; 6.0; 8.0 and 10.0 dS m -1 and three temperatures: 25 and 30°C constant and alternating 20-35°C. The physiological quality of seeds was evaluated using the following variables: germination, first count and the speed of germination index, length and dry weight of roots and hypocotyl. The results indicate that there is high probability of seed germination of Cryptostegia madagascariensis subjected to salt stress at constant temperature of 30°C and alternating 20-35°C, which enhances its invasive character.