Research in environmental sciences has found that the ergonomic design of human-made environments influences thought, feeling, and action. In the research reported here, we examined the impact of physical environments on dishonest behavior. In four studies, we tested whether certain bodily configurations—or postures—incidentally imposed by the environment led to increases in dishonest behavior. The first three experiments showed that individuals who assumed expansive postures (either consciously or inadvertently) were more likely to steal money, cheat on a test, and commit traffic violations in a driving simulation. Results suggested that participants’ self-reported sense of power mediated the link between postural expansiveness and dishonesty. Study 4 revealed that automobiles with more expansive driver’s seats were more likely to be illegally parked on New York City streets. Taken together, the results suggest that, first, environments that expand the body can inadvertently lead people to feel more powerful, and second, these feelings of power can cause dishonest behavior.