Purpose <p>This study aimed to investigate the relationship between sarcopenia and stress urinary incontinence (SUI) in postmenopausal women with and without osteoporosis and to identify independent predictors of SUI.</p> Methods <p>This cross-sectional study included 100 postmenopausal women aged 60–75 years, with 50 osteoporotic and 50 non-osteoporotic participants based on DXA T-scores. Sarcopenia was diagnosed using EWGSOP2 criteria. Muscle strength was assessed by handgrip and chair stand tests, and muscle mass was measured via bioelectrical impedance analysis. The presence of SUI was determined by self-reported symptoms. The impact of UI on quality of life was assessed using the Incontinence Quality of Life Questionnaire (I-QOL).</p> Results <p>Sarcopenia was more prevalent in the osteoporotic group than in controls (30% vs. 12%, <i>p</i> = 0.027). SUI was also more common among osteoporotic patients (50% vs. 24%, <i>p</i> = 0.013). In the osteoporosis group, probable sarcopenia was more frequent in women with SUI than in those without SUI (72% vs. 40%, <i>p</i> = 0.023), while the prevalence of definite sarcopenia did not differ significantly. In multivariate logistic regression, osteoporosis (OR = 3.519, 95% CI: 1.213–10.211, <i>p</i> = 0.021) and sarcopenia (OR = 3.313, 95% CI: 1.112–9.868, <i>p</i> = 0.031) were both significantly associated with SUI. No significant association was found between SUI and age, BMI, comorbidities, number of vaginal deliveries, or constipation. I-QOL scores were positively correlated with handgrip strength and negatively correlated with chair stand duration.</p> Conclusion <p>Sarcopenia and SUI were more prevalent in postmenopausal women with osteoporosis. Both osteoporosis and sarcopenia were independent risk factors for SUI. These findings highlight the importance of assessing muscle strength and pelvic floor function in postmenopausal women, particularly those with osteoporosis.</p> Clinical trials <p>ClinicalTrials.gov ID: NCT06655701.</p>