A complete record of the range of most species of zooplankton within river systems is rare. The calanoid copepod Eurytemora affinis has a relatively detailed description of its range in fresh waters, mostly because of its recent invasion into freshwater. Within the Ohio River, E. affinis has been documented twice, but these reports are from only a small section of the river. The objective of this paper is to describe the upstream dispersal of Eurytemora affinis in the Ohio River. Zooplankton samples were collected in four pools (Dashields, Montgomery, Racine, and Gallipolis) in the upper section of the Ohio River between September 2002 and September 2003. Eurytemora affinis was the dominant copepod in all four pools. Furthermore, copepodites and females carrying eggs were present, which suggests that E. affinis has established populations in the upper Ohio River. This extends the range to include, at minimum, the upper two-thirds of the Ohio River.