Background Osteosarcopenia is a recently described geriatric syndrome. Studies concerning its role on physical function are relatively few. Aim To evaluate the prevalence of osteosarcopenia and to analyze its relationship with physical function among postmenopausal women. Methods Demographic and clinical data, fracture risk, and osteosarcopenia risk factors of 140 postmenopausal women were evaluated between April 2018 and September 2018. Body composition and bone mineral density were measured by dual-energy X-ray absorbtiometry. Handgrip strength and physical performance test results were recorded. Sarcopenia was diagnosed according to the European Working Group on Sarcopenia in Older People, whereas osteopenia/osteoporosis was diagnosed according to the World Health Organisation criteria. Results The mean age of the patients was 64.1 +/- 8.9 years. Among the patients, 64.3% (n = 90) were found to be osteosarcopenic. Insufficient protein and calcium intake and low physical activity level were found to be the most frequent risk factors. When further analysis was done according to the osteosarcopenia, sarcopenia-only, and osteoporosis-only groups, osteosarcopenia group revealed the lowest body mass index, skeletal mass index, handgrip strength values, and physical performance test results. The handgrip strength was found to be a determinant of osteosarcopenia and each 1-unit decrease in handgrip strength increased the risk of osteosarcopenia by 1.162 times (95% CI 1.086-1.25). Conclusions The prevalence of osteosarcopenia is high among postmenopausal women. It is recommended to be aware of osteosarcopenia while managing osteoporotic patients, to use handgrip strength as a simple screening method, and to consider sarcopenia treatment as an important component of osteoporosis prevention and treatment.