Homeless adults have among the highest rates of cigarette smoking. Few studies have explored the potential of smoke-free policies as facilitators of smoking cessation or harm reduction among sheltered homeless adults. We focused on clients of a homeless shelter in San Diego, California. The facility prohibited smoking indoors and outdoors within five blocks of the building, and permitted smoking during four smoking breaks during the day in designated smoking zones away from the building. Current and former smokers who were residents of the facility were interviewed on smoking behaviors and attitudes toward these policies. Of the 170 ever smokers, 75.3% were current smokers. The average daily cigarette consumption was 6.6 cigarettes per day (SD 4.3). More than half of the participants (57.8%) attempted to quit smoking in the past year. Of the current smokers, three-fourths agreed that the facility policies were associated with their reduced consumption, and about half agreed that the policies were associated with either making a quit attempt or getting ready to quit completely. Sixty percent agreed that further restrictions on smoking, beyond the current policies, would be associated with increased interest in quitting smoking completely. Less than 10% agreed that they were unhappy to stay in the facility because of the policies. Findings suggest that smoke-free policies may not influence occupancy rates in shelters serving clientele with high rates of cigarette smoking. Smoke-free policies in homeless service settings present an important and un-tapped opportunity to reduce smoking behaviors among homeless adults.