Human activities are increasingly responsible for moving organisms far beyond natural dispersal distances and range boundaries. Here we describe the 1st documented instance of a slender salamander (genus Batrachoseps; B. attenuatus specifically) in Washington State, in the Seattle suburb of Kirkland. We molecularly identified this individual as belonging to a B. attenuatus clade in San Francisco, California. Beyond representing the 1st Batrachoseps in Washington, this is the 1st record of B. attenuatus introduced beyond its range limits in central and northern California, and the 1st record of the entire genus far beyond its geographic range. This specimen is also noteworthy because it was a gravid female that was exceptionally large, suggesting it could found a population on its own if one does not already exist, and that habitat conditions in a suburban region of the Pacific Northwest are suitable for this species. The Pacific Northwest is expected to be particularly suitable for the establishment of a diversity of introduced salamander species, and our work highlights the importance of proactive research and management to address species introductions.