This report presents the results of a study evaluating the greenhouse gas (GHG) emission changes that result from individuals participating in a carsharing organization. The principle of carsharing is simple: individuals gain the benefits of private vehicle use without the costs and responsibilities of ownership. Carsharing is most common in major urban areas where transportation alternatives are easily accessible. Individuals typically access vehicles by joining an organization that maintains a fleet of cars and light trucks deployed in lots located within neighborhoods, public transit stations, employment centers, and colleges/universities. In this study, the authors conducted a survey of carsharing members across the country to develop a robust estimate of GHG emission impacts resulting from carsharing. The results illustrate the annualized change in GHG emissions among members within the largest carsharing organizations across Canada and the United States. GHG emissions from transportation are lower due to carsharing. The average change in emissions across all respondents is -0.58 t GHG per household per year for the observed impact, and -0.84 t GHG per household per year for the full impact. However, it is important that this result is understood in the context of the broad diversity of carsharing impacts. While carsharing does facilitate lower emissions, the reduction is not generalizable across all members or even a majority of members. Rather, carsharing as a system facilitates large reductions in the annual emissions of some households, which compensate for the collective small emission increases of other households. The results also show that respondent households exhibit significant reductions in vehicle ownership after joining carsharing.