The tamoatá Hoplosternum littorale (Hancock, 1828) is an alien catfish to the São Francisco River basin. Although it has been registered along all of this hydrological system’s extension, including the segment located upstream of the Três Marias dam, up to now the species had not yet been detected in the Pará River sub-basin. Between the 19th and 28th of October 2009, 27 specimens were collected in this drainage system; over half of them captured in a highly polluted artificial reservoir. The results of the present study reinforce that the implementation of reservoirs and the pollution of the continental waters favor not only the expansion, but also the establishment of non-native teleosts with opportunist habits.