Luetzelburgia auriculata is used in the reforestation of degraded areas in Brazil due to its adaptation to the conditions of the country’s semiarid region. However, saline stress is one of the main abiotic factors with a negative impact on plant development. The aim of the present study was to evaluate the influence of the mass of Luetzelburguia auriculata seeds on tolerance to saline stress. The experiment was conducted with a completely randomized design in a 2 x 5 factorial scheme with two classes of seeds [light (< 0.35 g) and heavy (≥ 0.35 g)], from ten morphologically similar mother plants that showed natural variation in seed mass, and five salinity levels, distributed in four replicates of 25 seeds. We evaluated the following variables: germination rate; germination speed index; mean germination time; initial seedling growth; and fresh and dry mass of the shoots, cotyledons and roots. The data were submitted to analysis of variance. Means for seed classes were compared using the F-test and regression analysis was performed for NaCl levels. The increase in saline stress led to reductions in germination, root length, fresh and dry mass of the shoots, and the GSI, as well as a delay in MGT. Seedlings from heavy seeds (≥ 0.35 g) exhibited greater tolerance to salt stress than those from light seeds (< 0.35 g), due to lower occlusion caused by NaCl levels. Thus, heavy seeds of L. auriculata are more tolerant to salt stress and should be prioritized, especially in the presence of high salinity levels