Data described herein was collected by USGS personnel and the project funded by USGS. Northern snakehead specimens were collected from the Potomac River and its tributaries by regional natural resource management agencies in the course of their field investigations working with this priority invasive aquatic species. Specimens were provided to USGS for the purpose of conducting health related assessments of northern snakehead in the region, with approximately 90 specimens evaluated grossly and histologically for the presence of lesions and abnormalities. Data presented here was collected seasonally (spring through fall) in 2006 and from 2015 to 2017. Data for each specimen includes date and location of collection, morphometrics, gender (if known), and gross abnormalities, and histological lesions observed. This body of data is stored in spreadsheet format.