BACKGROUND: Bacillus Calmette-Guérin (BCG) vaccine-related complications are frequently observed in children in Oman. There are a few regional studies on BCG complications, but none from Oman. OBJECTIVE: Evaluate the spectrum of BCG-vaccine related complications and immune status in Omani children. DESIGN: Retrospective cross-sectional study. SETTING: Referral tertiary hospital. METHODS: Children aged younger than 13 years old and with complications of BCG vaccination recorded from 2006-2018 were included in this study. Clinical characteristics, treatment, immune workup and outcome were reviewed from hospital records. MAIN OUTCOME MEASURES: Different BCG vaccine-related complications categorized by the site of involvement. SAMPLE SIZE: 226. RESULTS: Of the 226 children had BCG-vaccine related complications, 99% received BCG vaccine immediately after birth. The median age of presentation was 4 months. The most common complication was isolated BCG lymphadenitis (85%, n=192), followed by BCG-related osteomyelitis (10.2%, n=23) and disseminated BCG infection (4.9%, n=11). The median age of presentation of disseminated BCG was 5 months, with different organs involved. Out of 11 children with disseminated BCG infection, 72.7% (n=8) had primary immune deficiency (PID), including chronic granulomatous disease (CGD, n=5), severe combined immunodeficiency (SCID) (n=2); 1 patient had Mendelian susceptibility to mycobacterial disease (IFNGR2 deficiency); 2 patients with PID not yet identified and the 1 with a non-specific PID had blood or saliva samples sent for whole-exome sequencing. CONCLUSION: Because of the spectrum of BCG vaccine-related complications, including the most severe in children with PID, we suggest that delaying the BCG vaccine from birth to 6 months may prevent disseminated BCG diseases and their complications in children with PID because any PID will have been identified before 6 months. Further studies are needed to guide this recommendation. LIMITATIONS: Single center-based study that may not provide a full overview of all BCG vaccine-related complications in Oman. Unavailability of details of some microbiological results and an inability to determine the detailed management for all patients. CONFLICT OF INTEREST: None.