This study aimed to comparatively analyze the main morphological and histomorphometric characteristics of ovaries and testicles from Astyanax lacustris (Lutken, 1875) and Psellogrammus kennedyi (Eigenmann, 1903). The fish were obtained between April 2014 and March 2015, in Monte Alegre Reservoir (Salgueiro, Pernambuco). In total, 240 individuals were macroscopically analyzed and, from these, 126 gonads were histologically analyzed. During the period, A. lacustris presented four different gonadal stages and P. kennedyi displayed three. For both species, in every month, vitellogenic oocytes were detected macroscopically and, microscopically, only previtellogenic oocytes were visualized. The diameter of vitellogenic oocytes was higher (471.68 mu m+/-160.55; p<0.05) for females of A. lacustris. The diameter of the seminiferous tubules (114.68 mu m+/-34.57; p<0.05) and the height of the germinal epithelium (18.75 mu m+/-5.47; p<0.05) were higher for P. kennedyi. The mature testes in A. lacustris showed germinal epithelium with better delimited edges, when compared to P. kennedyi. The macroscopic observations presented that greatest values of the gonadosomatic index (GSI) of both species coincided with the period of higher precipitation (between November 2014 and May 2015) in the region. Finally, from the macro and microscopic observations, it was concluded that the two species present partitioned spawning with asynchronous oocyte development.