Background: Bertolotti syndrome is a differential diagnosis in back pain. We know little about it in Uganda. This study aimed to describe the prevalence, clinical and radiological patterns of Bertolotti syndrome and functional disability associated with it.Methods: We did a descriptive cross-sectional study at the spine outpatients’ clinic of Mulago National Referral Hospital. We screened patients with chronic low back pain for lumbosacral transitional vertebrae over four months and classified them according to Castellvi. We collected demographics, clinical symptoms, and functional disability data and summarized it descriptively.Results: Out of 385 patients, we identified 39 with Bertolotti syndrome. The prevalence and the median age were at 10.1% and 49 years respectively, with most patients being females (66.7%) in the age range of (36 to 50) years, the pain started during the age range of 31-40. The commonest and least were type IIA (20.5%) and type IV (10.3%), respectively. Most patients (66.3%) had radicular symptoms, mainly the toe extension nerve root. The average visual analog scale was 6.3. However, most patients suffered from mild- to moderate disability (66.7%).Conclusion: Bertolotti syndrome is common and functionally debilitating. We should consider it in the differential diagnosis of chronic low back pain. Keywords: Bertolotti syndrome; Transitional vertebrae; Functional disability.