Characterisation and reproduction studies of Amazonian species are extremely important for the recovery and preservation of this biome. The objective of this study was to morphologically characterise the fruits and seeds of Enterolobium contortisiliquum, as well as to verify the influence of seed mass and methods for breaking dormancy. Two evaluation periods consisting of 100 fruits and 500 seeds were analysed for morphological parameters. An experimental design of a complete randomised 2 × 3 × 3 factorial scheme was used to assess the effect of time in storage, mass and breaking dormancy. The important factors consisted of two periods (one and five months after seed collection), three classes of seed mass (< 0.877 g, 0.887-1.09 g and > 1.09 g) and two methods for breaking dormancy (sulphuric acid and mechanical scarification + control group) were identified. The evaluated parameters were germination, germination speed index, stem diameter, average germination time, radicle length, seedling height and the fresh and dry weights of root, shoot and total biomass. Mechanical scarification and sulphuric acid immersion promoted breaking dormancy in seeds of E. contortisiliquum, while the medium and large seeds showed better initial development. Mechanical scarification is recommended for breaking the seed dormancy of this species.