Herein we present evidence of the first observation of YOY Paralichthys dentatus (Summer Flounder) in the Saco River estuary, ME, in June of 2012. A possible explanation for the occurrence of YOY summer flounder in this region could be range expansion, which may have destructive effects on southern Maine estuary systems. As active predators, Summer Flounder have the potential to exploit locally abundant fishes, including Pseudopleuronectes americanus (Winter Flounder) and Ammodytes americanus (American Sand Lance).