Introduction Addressing smokers who smoke in a voluntary smoke-free area is vital to its successful implementation. Many people perceive barriers in addressing smokers due to fear of negative responses. Insights in actual responses are currently lacking. Methods This is an observational field study at the voluntary smoke-free zone surrounding the Erasmus MC and two schools in Rotterdam, the Netherlands. In the first month after implementing the zone, Erasmus MC representatives performed rounds to address smokers who were smoking inside the zone. Four people observed addressors for two weeks then they also addressed the smokers. Smokers were classified as employees, patients, students, or other. We noted whether smokers were addressed directly or indirectly, and their verbal and behavioral responses to being addressed. Differences between the responses of the groups were assessed using chi-squared tests. Results In all, 331 smokers were observed of whom 73% were addressed directly. Most verbal reactions were positive (46%) or neutral (18%). Employees were more likely to respond guiltily, whereas patients more often responded angrily than the others. After being addressed, the majority of smokers either extinguished their cigarette (41%) or left to continue smoking outside the smoke-free zone (34%). Conclusions Most smokers showed a positive or neutral response when being addressed about smoking inside the smoke-free zone and the majority adapted their behavior to comply with the policy. These findings may help decrease barriers for those in doubt about addressing smokers that fail to comply with a smoke-free policy.