Introduction: Osteoporosis is a major health problem worldwide. In Asia, few studies have measured knowledge, attitude and practices (KAP) of osteoporosis. This study aimed to determine the KAP of osteoporosis, including the main factors influencing attitude towards osteoporosis, and the relationship between osteoporosis knowledge, attitude, and practices among adults in Kuala Lumpur, Malaysia. Methods: A cross-sectional study via a self-administrated KAP questionnaire was carried out among 232 respondents aged 21 to 50 years in Kuala Lumpur. Random sampling was applied to select five districts in Kuala Lumpur, while convenient sampling was used for recruitment of apparently healthy subjects from community and institutional settings. The data were analysed using Mann-Whitney, Kruskal-Wallis, Chi-Square, Spearman Correlation and multiple logistic regression tests. Results: The findings indicate a moderate level of knowledge and attitude towards osteoporosis prevention with median scores of 51.6% and 68.6%, respectively. Osteoporosis knowledge varied significantly with gender, educational level and household income (p<0.05). Furthermore, attitude was significantly different in relation to educational level and household income. Based on the multiple logistic regression test, relatives and friends appeared to be the most significant factor influencing attitude (R=0.319, p<0.0001). Poor dietary and lifestyles practices were indicated, and a significant relationship was found between practice of weight-bearing activities and educational level (p<0.05). A significant correlation was found (ρ=0.348, p<0.0001) between knowledge and attitude, while no relationship was noted between knowledge and practice of weight-bearing activities or attitude and practice of weight-bearing activities. Conclusion: Knowledge played a significant role in affecting attitudes towards osteoporosis. However, understanding of osteoporosis is still at a moderate level. Friends and family were the most influential factor.