This study presents a list of species from igarapés tributaries of the rio Acre, Acre State, Brazil. Fish assemblages were sampled in October 2009, August and October 2010, using standard ichthyological gear, along fifteen sampling sites. A total of 11,395 specimens, distributed in 94 species, 24 families and six orders were collected. The most species-rich orders were Characiformes with 45 species (48.4%) and Siluriformes with 33 species (34.7%); from which Serrapinnus gr. microdon (22.4%), Otocinclus vittatus (20.4%), Phenacogaster pectinatus (10.9%), Brachychalcinus copei (5.8%) and Knodus sp. (5.3%) represented 64.8 % of the specimens captured. The species accumulation curve does not present a stabilization tendency, indicating that, additional sampling can increase the number of species. This study has a high importance for the knowledge of the rio Acre fish fauna composition and adds 52 new records of species to the fish fauna of the rio Purus.