One proposed solution to prolonged emergency department (ED) wait times is a publicly available website that displays estimated ED wait times. This could provide information to patients so that they may choose sites with low wait times, which has the potential to smooth the overall wait times in EDs across a health system. We describe the effect of a novel city-wide ED wait time website on patient volume distributions throughout the city of Hamilton, Ontario, Canada. We compared the number of new patients arriving every 15 minutes during 2 separate time periods—before and after a publicly viewable wait time website was made available. For each ED site, the effect of the posted wait time was measured by assessing its association with the total number of patient arrivals in the subsequent hour at the same site and at all other sites in Hamilton. Linear models showed clinically modest changes in patient volumes when wait times changed. However, nonlinear models showed that a 60-minute increase in wait time at a site was associated with 10% fewer patients presenting over the next hour. Larger negative associations were observed at community hospitals and urgent care centers. Increases in wait times at a given site were also associated with increased patient volumes at other sites in the system. After the implementation of a public wait time website, elevated wait times led to fewer patients at the same site but more patient visits at other sites. This may be consistent with the wait time tracker inducing patients to avoid sites with high wait times and instead visit alternate sites in Hamilton, but only when wait times were very high.