The role of headwater wetlands in shaping amphibian presence and activity in small catchments is poorly defined and requires better understanding in order to conserve amphibians in this unique wetland setting. We assessed amphibian diversity and seasonal activity in headwater wetlands and the adjacent upland forest in Hancock County, Maine, USA, using pitfall trapping, visual encounter surveys, and cover board arrays. We captured 659 individuals over 20,626 trap nights in trap arrays and completed 106 visual encounter survey transects documenting 593 individuals in 2004 and 2005. We found 12 of the 17 amphibian species known to occur in Maine. Amphibians made extensive use of both upland and wetland ecosystems, including ‘small’ (< 0.36 ha) headwater wetlands. Time spent in wetland or upland habitats was highly variable among species with differences in captures between uplands and wetlands occurring during only two (April and June) of seven monitoring periods spanning from April to October. Observed species-specific activity in each ecosystem differed depending on the method used even during coincident time periods. For example, we often failed to detect the common terrestrial anuran Lithobates sylvaticus using visual encounter surveys however pitfall traps routinely caught individuals traveling through the forest. Our results suggest that the presence of isolated headwater wetlands extend amphibian activity from riparian zones into adjacent terrestrial forests. In addition, the timing of surveys is critical in order to accurately estimate populations, since differences in as few as two weeks may lead to imprecise conclusions regarding species presence or abundance.