Variation in primary productivity has been described for an extensive range of natural systems and may lead to remarkable bottom-up effects on consumer communities at higher trophic levels. During a standardized sampling of the small mammal assemblage in the Reserva Florestal Morro Grande, SP, Brazil, we documented a bamboo blooming followed by an increase in abundance of small mammals. Here we described the effects of this blooming of the assemblage of small mammals and evaluated if (i) the abundance of frugi-/granivore species is affected more strongly than the abundance of insect-/omnivore species and (ii) due to the massive food availability in the habitat (bamboo seeds), body mass index of one of the affected species, the rodent Euryoryzomys russatus, will increase after the bamboo blooming. Although some species became more abundant, the difference was not related to species diet. We did find a significant increase in the body weight of Euryoryzomys russatus after the bamboo blooming. We emphasize that an infrequent and poorly known event like bamboo blooming can have a major impact on rodent population dynamics, regardless of the species diet, increasing abundance, and weight bottom-up controlled by the massive availability of food resources.