Nonnative species that cause damage to ecosystems to which they are introduced are considered in-vasive. Restoration of the original ecosystem after an invasive population has established is expensive and difficult but more likely to succeed when invasions are discovered early. Containment efforts to prevent the spread of known invasions also benefit from earlier knowledge of invaded sites. Environ-mental DNA (eDNA) techniques are emerging as a tool that can identify invasive species at a distinctly earlier time point than traditional methods of detection. I collected water samples from eight sites not known to be invaded by the freshwater New Zealand mud snail (NZMS). After filtering these samples to collect eDNA, I used a species-specific probe with qPCR to identify NZMS eDNA. I found evidence for NZMS invasion at five of the eight sites, with later physical confirmation of mud snails at one of these sites. This study is the first example of successful application of eDNA to detect new invasions of the freshwater New Zealand mud snail, setting the stage for further monitoring of at-risk sites to de-tect and control new invasions of this destructive snail.