Abstract Fish can undergo changes in their life-history traits that correspond with local demographic conditions. Under range expansion, a population of non-native fish might then be expected to exhibit a suite of life-history traits that differ between the edge and the centre of the population’s geographic range. To test this hypothesis, life-history traits of an expanding population of round goby, Neogobius melanostomus (Pallas), in early and newly established sites in the Trent River (Ontario, Canada) were compared in 2007 and 2008. Round goby in the area of first introduction exhibited a significant decrease in age at maturity, increased length at age 1 and they increased in GSI from 2007 to 2008. While individuals at the edges of the range exhibited traits that promote population growth under low intraspecific density, yearly variability in life-history traits suggests that additional processes such as declining density and fluctuating food availability are influencing the reproductive strategy and growth of round goby during an invasion.