The reproductive cycle and gonadal development of Donax striatus from a sandy beach in Ajuruteua, Amazon region, were studied. Monthly sampling took place from March 2015 to April 2016. Histological analysis was performed on 420 individuals, and the oocyte diameters were determined from histological sections and used to determine the reproductive period. The population showed a balanced sex ratio (1:1) with a size at first maturity of 10.9 mm in males and 8.9 mm in females. The population showed r-strategist characteristics and continuous spawning, and the reproductive cycle showed no seasonal variation or significant relation with any environmental parameter. The organic matter was significantly higher in the rainy season. According to the generalized linear model analysis (GLM), only the condition index (CI) had a significant relationship with the organic matter of the sediment. The type of reproductive strategy adopted by D. striatus corroborates the global breeding hypotheses for species of tropical environments. For conservation, it should be recommended to harvest this species at a shell length above 13 mm.