Aims Despite the importance of adherence in increasing efficacy of treatment, controlling osteoporosis, and reducing costs of treatment, compliance with osteoporosis medications is less than expected. The aim of this study was to determine treatment adherence among women with osteoporosis. Participants & Methods This qualitative research was conducted in Sanandaj, Iran in 2016. Participants were chosen through purposeful sampling method. Fifteen women with age 50 years and over, diagnosed with osteoporosis for at least 6 months, T-score below-2. 5, and previously prescribed osteoporosis medication were selected. To understand the women’ s views, semi-structured interviews were recorded, typed, and analyzed using content analysis. Criteria of credibility, confirmability, dependability, and transformability were used in order to verify the accuracy and consistency of the data. Findings From data analysis, two main themes (Factors related to adherence and factors related to non-adherence) and 10 sub-themes (Social supports, motivational factors, symptomatology, medication side effects, psychological characteristics, economic status, cultural beliefs about illness and treatment, patient’ s dissatisfaction, lack of knowledge, and medication factors) were identified. Conclusion Treatment adherence is multi-factorial including individual, psychological, social, economic, and cultural factors. Improving health literacy and increasing awareness about the benefits of medications may promote greater medication adherence and improve clinical outcomes for patients with osteoporosis.