The Arkansas Darter (Etheostoma cragini) is a threatened species in Kansas and was a candidate for threatened status under the Endangered Species Act (1973). The Arkansas Darter's distribution in Kansas includes the Cimarron River basin of southwestern Kansas, the Arkansas River basin in southcentral Kansas, and the Spring River basin (SRB) in southeastern Kansas. Historical surveys in the SRB during the 1960s and 1990s did not detect the Arkansas Darter in the Cow Creek watershed, which is the northernmost tributary of the Spring River. Here we report detection of the Arkansas Darter in three streams of the Cow Creek watershed during August and September 2017, including an unnamed tributary of Cow Creek (eight individuals), the Cow Creek mainstem (one individual), and the Long Branch (five individuals). Although Arkansas Darters were detected in three different streams, collections were all within 1.5 river kilometers of one another. Further, the species was not detected at 26 other locations in the Cow Creek watershed during 2017, indicating a restricted distribution for this fish in this system. This range extension for the Arkansas Darter in the SRB of Kansas may have conservation implications.