As public housing agencies and other low-income housing providers adopt smoke-free policies, data are needed to inform implementation approaches that support compliance. Focused ethnography used including qualitative interviews with staff, focus groups with residents, and property observations. Four low-income housing properties in Massachusetts, 12 months postpolicy adoption. Individual interviews (n = 17) with property staff (managers, resident service coordinators, maintenance, security, and administrators) and focus groups with resident smokers (n = 28) and nonsmokers (n = 47). Informed by the social-ecological model: intrapersonal, interpersonal, organizational, and community factors relating to compliance were assessed. Utilized MAXQDA in a theory-driven immersion/crystallization analytic process with cycles of raw data examination and pattern identification until no new themes emerged. Self-reported secondhand smoke exposure (SHSe) was reduced but not eliminated. Challenges included relying on ambivalent maintenance staff and residents to report violations, staff serving as both enforcers and smoking cessation counsellors, and inability to enforce on nights and weekends. Erroneous knowledge of the policy, perception that SHSe is not harmful to neighbors, as well as believing that smokers were losing their autonomy and being unfairly singled out when other resident violations were being unaddressed, hindered policy acceptance among resident smokers. The greatest challenge to compliance was the lack of allowable outdoor smoking areas that may have reduced the burden of the policy on smokers. Smoke-free policy implementation to support compliance could be enhanced with information about SHSe for smokers and nonsmokers, cessation support from external community partners, discussion forums for maintenance staff, resident inclusion in decision-making, and framing the policy as part of a broader wellness initiative.