BACKGROUND Little is known about inflammatory bowel disease (IBD) burden and its impact on bone mineral density (BMD) among adult patients in Saudi Arabia. To the best of our knowledge, our study is the only study to give an update about this health problem in adult Saudi patients with IBD. IBD is a great risk factor for reduced BMD due to its associated chronic inflammation, malabsorption, weight loss and medication side effects. Consequently, screening for reduced BMD among patients with IBD is of utmost importance to curb and control anticipated morbidity and mortality among those patients. AIM To assess the relationship between IBD and BMD in a sample of adult Saudi patients with IBD. METHODS Ninety adult patients with IBD - 62 Crohn’s disease (CD) and 28 ulcerative colitis (UC) - were recruited from King Fahad Specialist Hospital gastroenterology clinics in Buraidah, Al-Qassim. All enrolled patients were interviewed for their demographic information and for IBD- and BMD-related clinical data. All patients had the necessary laboratory markers and dual-energy x-ray absorptiometry scans to evaluate their BMD status. Patients were divided into two groups (CD and UC) to explore their clinical characteristics and possible risk factors for reduced BMD. RESULTS The CD group was significantly more prone to osteopenia and osteoporosis compared to the UC group; 44% of the CD patients had normal BMD, 19% had osteopenia, and 37% had osteoporosis, while 78% of the UC patients had normal BMD, 7% had osteopenia, and 25% had osteoporosis ( P value < 0.05). In the CD group, the lowest t -score showed a statistically significant correlation with body mass index (BMI) ( r = 0.45, P < 0.001), lumbar z -score ( r = 0.77, P < 0.05) and femur z -score ( r = 0.85, P < 0.05). In the UC group, the lowest t -score showed only statistically significant correlation with the lumbar z -score ( r = 0.82, P < 0.05) and femur z -score ( r = 0.80, P < 0.05). The ROC-curve showed that low BMI could predict the lowest t -score in the CD group with the best cut-off value at ≤ 23.43 (m/kg 2 ); area under the curve was 0.73 (95%CI: 0.59–0.84), with a sensitivity of 77%, and a specificity of 63%. CONCLUSION Saudi patients with IBD still have an increased risk of reduced BMD, more in CD patients. Low BMI is a significant risk factor for reduced BMD in CD patients.