The fauna and community structure of the helminths of two sympatric sigmodontine rodent hosts, Akodon montensis (Thomas, 1913) and Oligoryzomys nigripes (Olfers, 1818) (Rodentia, Cricetidae) were studied in two areas of an Atlantic Forest reserve, the Serra dos Órgãos National Park in Petrópolis and Teresópolis municipalities, state of Rio de Janeiro, Brazil. During the study, 127 rodents were collected, among which 63 were parasitized (approximately 50%). The helminths recovered from A. montensis were the nematodes Protospirura numidica criceticola, Stilestrongylus aculeata, Stilestrongylus eta, Stilestrongylus lanfrediae and Trichofreitasia lenti; the trematode Canaania obesa and the cestode Rodentolepis akodontis. Oligoryzomys nigripes was infected by Avellaria sp., Guerrerostrongylus zetta, T. lenti and S. lanfrediae. Complete host specificity was observed in all helminth species only in Petrópolis; although T. lenti and S. lanfrediae were shared between host species in Teresópolis. Stilestrongylus aculeata, S. eta and S. lanfrediae had the greatest abundance, i.e. considering all hosts, and intensity, i.e. considering only infected hosts, in the study. Stilestrongylus lanfrediae and G. zetta were the most prevalent species. Guerrerostrongylus zetta and S. lanfrediae had higher abundance and prevalence in adult hosts. The latter species also had higher abundance and prevalence in male hosts. Stilestrongylus aculeata and S. eta had higher prevalence in young female hosts, and T. lenti, higher abundance in males and higher prevalence in adult females of A. montensis. Only the helminth community of O. nigripes in Teresópolis followed a nested pattern of species distribution. All the other helminth communities in A. montensis and O. nigripes had random patterns of species distribution. The results suggest the existence of intrinsic characteristics between hosts and parasites as well as different patterns of associations in those interactions with the environment.