We studied the reproductive phenology of five endemic Eleutherodactylus species that coexist in a mountain rainforest in Cuba and estimated their sex ratios at immature and mature stages. We tested the hypothesis that in Neotropical humid sites, reproductive activity in sympatric species will vary in the time of occurrence so that there is no complete temporal overlap. We also investigated whether the length of the breeding season was associated to relative testes size as a proxy for male–male competition. We inferred reproductive phenology from seasonal variation in the number of sexually active individuals, their gonad developmental stage, and male vocal activity from January 2003 to March 2004. Our data do not support the hypothesis of temporal segregation in reproduction for this assemblage because we found a prolonged reproductive pattern in the five species, but there was decreased breeding intensity in the cooler months (November–February). This deduction is supported by a drop in the weight of the ovaries and the number of vitellogenic follicles, absence of mature females or reduction of their abundance, and disappearance of male vocal activity in the winter. We found differences in relative testes size among species, which were not related to differences in the length of the breeding season, but rather to interspecific differences in sex ratio.