Blanding’s turtles are a Threatened species in New York, largely due to habitat degradation. In 1996-97 1 ha of wetland and 3 ha of nesting habitat were constructed to mitigate the loss of habitats destroyed during a school expansion in Dutchess County, NY. Organic sods with intact herbaceous and shrubby vegetation were moved from the destroyed wetland to the constructed wetlands to accelerate development of the flooded, shrubby, organic-soil pools favored by Blanding’s turtle in Dutchess. The project included a 1300 m fence on two sides of the mitigation area with one-way turtle “gates” to reduce the risk of turtles leaving the area and entering parking lots or highways. We collected one season of pre-construction data and are now in the eleventh year of post-construction study of turtle activities, hydrology, soils, and vegetation. Adult Blanding’s turtles immediately used constructed wetlands in the nesting season and summer, and nested on constructed upland habitats. In constructed wetlands, Blanding’s turtles were associated with less cover and warmer water than in nearby natural wetlands. Constructed wetlands provided basking and foraging habitat in the spring and early summer, and staging or rehydrating areas for nesting females. Nesting females selected soils with more gravel in wetter spring seasons and more sand in drier seasons; hatchling productivity and length/weight ratio did not differ among years. Adult use of constructed and natural wetlands has been closely related to water levels. Long-term data addressing several aspects of a turtle population and its ecosystem demonstrate changing behavior in relation to environmental factors and provide a better basis for conservation management.