The phylogeny of California Slender Salamanders (Batrachoseps attenuatus), which inhabits Northern California's Coast Ranges and Sierra Nevada foothills, was previously investigated by Martínez-Solano et al. (2007), who recovered a monophyletic species that contained five geographically cohesive major clades. However, a population isolate of B. attenuatus found in the Sutter Buttes, a geographically isolated volcanic mountain range within the Sacramento Valley, was not available in their phylogenetic analysis. We sequenced the ∼780-base pair segment of the mitochondrial DNA cytochrome b (cytb) gene used in Martínez-Solano et al. (2007) to examine the phylogenetic placement of this isolated population within the B. attenuatus complex. Our results, based on a single mitochondrial marker, indicate that the Sutter Buttes population of B. attenuatus is genetically distinct and falls within the Martínez-Solano et al. (2007) “East Bay/Sierra subclade” that, in turn, is nested within their “Eastern” major clade. Although we cannot accurately estimate how long the Sutter Buttes population has been isolated, B. attenuatus was likely able to colonize the Sutter Buttes during pluvial Pleistocene interglacials when more contiguous woodlands may have opened dispersal corridors across the Great Central Valley.