Polycystic ovary syndrome (PCOS) occurs in approximately 7 to 18% of reproductive-aged women worldwide and is characterized by oligo/amenorrhea, hyperandrogenism, and/or polycystic ovaries. Women with PCOS are at higher risk of poor physical and mental health outcomes. Up to 80% of women with PCOS have reported BMI ≥25 kg/m2, leading researchers to hypothesize that obesity contributes to the development of PCOS. Although poor diet and physical inactivity are known contributors of obesity, it remains uncertain whether these activities can predict the development of PCOS features. Weight loss interventions are the first recommendation in treating reproductive and metabolic symptoms of PCOS, yet adherence with these interventions varies greatly across PCOS studies. To encourage behavior change, it is essential to understand: 1) the associations between diet and physical activity (PA) behaviors with PCOS and 2) the health-related knowledge and beliefs associated with PCOS. This dissertation addresses these research gaps by investigating the cross-sectional associations between PCOS and dietary and physical activity behaviors, as well as knowledge, and beliefs. Our published narrative review (Chapter 1) summarizes the current evidence of the health-related behaviors – PCOS link and identifies gaps in the literature to inform the studies conducted in Parts 1 and 2 of this dissertation. Two approaches were used in Part 1 to investigate the link between health-related behaviors with combined and/or isolated features of PCOS. Chapter 2 presents a secondary data analysis using data from the longitudinal cohort, Coronary Artery Risk Development in Young Adults (CARDIA) Women’s Study. We show that diet quality was associated with PCOS, and that this association varied by race. When macro- or micronutrient intake were considered individually, there were no differences between women with and without PCOS. Similarly, there were no differences in PA by PCOS status. Results from our prospective case-comparison study (Assessment of Dietary Intake and Physical Activity in Women with and without PCOS) in Chapter 3 confirmed that diet, but not PA, was linked to PCOS status. These findings suggest that some aspects of diet could serve as targets for tailored PCOS interventions. Part 2 explored associations between health-related knowledge and beliefs with PCOS status. We developed and validated two instruments that were distributed to reproductive-aged women in the United States. Findings from Chapter 4 (Instrument for PCOS: Knowledge, Health-Related Beliefs, and Self-Efficacy) demonstrate that women with PCOS had less favorable health-related beliefs than the comparison group, but reported similar self-efficacy in performing salubrious diet behaviors. In Chapter 5 (Instrument for PCOS: Medical Experiences), we report that specific domains of trust and social support directed toward healthcare professionals differed between women with and without PCOS, thereby identifying factors that could improve the physician and PCOS patient relationship. Collectively, this dissertation integrates physiological, sociological and epidemiological concepts with nutrition in order to contribute to the development of effective behavioral interventions for PCOS patients.