A study on the ecological patterns characterizing the community of arthropods parasitic of sigmodontine rodents was carried out in an area that represents the environmental conditions of the Argentinean Chaco. Four species of mites (Laelapidae and Macronyssidae), one of tick (Ixodidae), and five of fleas (Rhopalopsyllidae and Stephanocircidae) were collected on six species of sigmodontine rodents (Cricetidae: Sigmodontinae). As a generality, the parasite taxa studied in this work presented similar patterns of host specificity and aggregation. With the exception of laelapid mites, the remainder taxa exhibited low levels of host specificity. All parasites show a tendency toward aggregation, and the pattern of host usage appears to be constant on geographical scales. Ticks (immature stages of A. tigrinum) were found on sigmodontines during the whole year with peaks of abundance in different seasons, while mites and fleas were detected from late summer to late spring, with the peak of abundance in winter. A significant positive correlation between monthly abundance of rodents and monthly abundance of mites and fleas was found, suggesting that the pattern of seasonality of these two taxa could be determined by the seasonal abundance of hosts. Finally, the potential epidemiological implications related to the lack of strict host specificity showed by most of the parasites studied in this work were discussed.