Carsharing has grown considerably in North America during the past decade and has flourished within metropolitan regions across the United States and Canada. The result has been a new transportation landscape, which offers urban residents an alternative to automobility without car ownership. As carsharing has expanded, there has been a growing demand to understand its environmental impacts. This paper presents the results of a North American carsharing member survey (N = 6,281). The authors establish a “before-and-after” analytical design with a focus on carsharing’s impacts on household vehicle holdings and the aggregate vehicle population. The results show that carsharing members reduce their vehicle holdings to a degree that is statistically significant. The average vehicles per household of the sample drops from 0.47 to 0.24. Most of this shift constitutes one-car households becoming carless. The average fuel economy of carsharing vehicles used most often by respondents is 10 miles per gallon (mpg) more efficient than the average vehicle shed by respondents. The median age of vehicles shed by carsharing households is 11 years, but the distribution covers a considerable range. An aggregate analysis suggests that carsharing has taken between 90,000 to 130,000 vehicles off the road. This equates to 9 to 13 vehicles (including shed and postponed auto purchases) for each carsharing vehicle.