One of the theories that have been proposed in Canada’s oil sands area is that early exposure of fish to oil sands related compounds in rivers may cause effects later in life, even after the fish grow and move to larger rivers far from oil sands. The aim of this study was to characterize potential effects of natural oil sands sediments on the fathead minnow in a lifecycle test that assesses growth, maturation, and reproduction. Fish were exposed for 22 days, from egg fertilization to 16 days post hatch (dph) to 1 or 3 g/L of river sediment from 3 different sites: a control site (alkyl PAHs = 3 ng/g wet weight sediment), one site influenced by the natural oil sands (alkyl PAHs = 6200 ng/g), and one site with natural oil sands that is near mining development (alkyl PAHs = 4500 ng/g). After this embryo-larval exposure period, fish were transferred to clean water flow-through tanks and raised to adulthood. Deformities and reduced weight were observed during the exposure period, but growth recovered over time in clean water. Reproduction was decreased (significantly fewer eggs laid) in fish exposed to 3 g/L sediment from the river near mining development. However, although there were effects on the early-exposed fish, there were no effects in their offspring as the F1 showed good hatching, survival, and very low incidences of deformities.