Terrestrial Isopods were sampled in four protected Atlantic Forest areas located in Serra do Mar, state of São Paulo, southeastern Brazil. A total of 2,217 individuals of six species (Atlantoscia sp., Benthana werneri, Pseudodiploexochus tabularis, Pudeoniscus obscurus, Styloniscus spinosus and Trichorhina sp.) were captured in pitfall traps. The exotic species S. spinosus is recorded for the first time for the Americas. Another introduced species, P. tabularis, previously recorded only from the state of Rio Grande do Sul, had its geographic distribution extended to the state of São Paulo. The most abundant isopods in this study belong to an undescribed species of Atlantoscia. [ABSTRACT FROM AUTHOR]