© 2015, © 2015 SAGE Publications. While corporate sustainability has been defined as an approach that creates long-term value with minimum environmental damage, there is still little understanding of the time horizon over which improved environmental performance leads to improved financial performance. We investigate the relationship between environmental and financial performance under increasing likelihood of environmental regulation. We leverage longitudinal data for 1,095 U.S. corporations from 2004 to 2008, a period of increasing activity for climate change legislation, in order to estimate the effect of greenhouse gas emissions on short- and long-term measures of financial performance. We find that during this period, improving corporate environmental performance causes a decline in an indicator of short-term financial performance, return on assets. Nonetheless, investors see the potential long-term value of improved environmental performance, manifested by an increase in Tobin’s q. These results suggest that limited uptake of proactive strategies may in part be attributable to short-term financial performance targets that guide managerial decision making.