INTRODUCTION: The aim of this study was to validate the effectiveness of the osteoporosis self-assessment tool for Asians (OSTA) in the screening and diagnosis of osteoporosis in men aged over 50 years and postmenopausal women in the northern Vietnam population. MATERIALS AND METHODS: This study included 8077 participants (7044 postmenopausal women and 1033 men aged over 50) who attended health examinations at the National Institute of Nutrition, Vietnam, from 2010-2019. Osteoporosis is defined by a T-score ≤ -2.5 at the femoral neck, total hip, or L1-L4. OSTA scores were assessed for identifying osteoporosis via receiver operating characteristic (ROC) curves. The optimal cut-off points, sensitivity, specificity, and areas under the ROC curves (AUCs) were determined. RESULTS: The study showed that the prevalence of osteoporosis was 13.4% in men and 25.5% in women. In women, a higher BMI and OSTA scores decreased the OR of osteoporosis (all p-values <
0.002). In men, a higher BMI decreased the OR of osteoporosis (p-value <
0.002). The results showed that the OSTA value was -1 which had a sensitivity of over 70% in both men and women. The OSTA value was -4 which had a sensitivity of over 90% and specificity of over 80% in both men and women. The optimal OSTA value was -3 which had a sensitivity of over 90% and a specificity of over 80% in both men and women. CONCLUSIONS: The OSTA might be a simple tool for the screening and diagnosis of osteoporosis in Vietnamese postmenopausal women and men aged over 50 years.