Mitchell's satyr (Neonympha mitchellii mitchellii) is a restricted fen species currently listed as endangered by the U.S. Fish and Wildlife Service and is considered one of the rarest butterflies in North America. The objectives of this study were to estimate population size, determine distribution within the study site and characterize habitat use for this important species. A mark-release-recapture study conducted at a prairie fen in Jackson County, Michigan, yielded a total population estimate of 1106 individuals. Most N. m. mitchellii were captured at the interface of open fen or sedge meadow and tamarack/hardwood forest within 3 m of woody vegetation. Distribution of N. m. mitchellii within the fen was clumped. The longest distances flown by males and females were 511.8 m and 344.8 m, respectively. Minimum home range values were 0.22 ha for males and 0.07 ha for females. Compared with prior studies on two populations in southwestern Michigan, these individuals flew significantly farther and had much larger population and home range sizes. This new information is critical for the conservation of the species and provides evidence that individuals may be capable of dispersing to new areas if linkages exist between isolated colonies.