Background: Tuberculosis (TB) is one of the most important infectious diseases worldwide. Bacillus Calmette-Guerin (BCG) is a live attenuated vaccine, entered into the childhood immunization program by the World Health Organization (WHO) in 1974 to prevent TB. One of the relatively common complications of BCG vaccination is regional lymphadenitis. Objectives: This study aimed to determine the lymphadenitis incidence in BCG-vaccinated children in southwest Iran. Methods: In a prospective descriptive study, infants born from March to June 2017 were evaluated for BCG vaccine complications at two, four, six, nine, and 12 months of age in Ahvaz, southwestern Iran. Results: The study enrolled 1,506 infants (794 males and 712 females). Among the vaccinated infants, four (0.26%) had injection site reactions, and 106 (7.03%) presented lymphadenitis (66 males and 40 females). The lymphadenitis rate was significantly higher in males than in females (P = 0.024). The mean age at presentation was 4.28 ± 0.79 months. Suppurative lymphadenitis was seen in 53 (50%) cases and nonsuppurative lymphadenitis in 53 (50%) cases. About 80% of nonsuppurative lymphadenitis resolved entirely or partially after a one-year follow-up. Of 53 cases with suppurative lymphadenitis, 46 (43.4%) developed spontaneous drainage, and seven (6.6%) were drained by needle aspiration. No significant relationship was found between the BCG inoculation site and lymphadenitis rate. No other complications such as osteomyelitis or disseminated BCG infection were observed after one year of follow-up. Conclusions: The relatively high incidence of BCG lymphadenitis in this study may be due to the vaccine strain, young vaccinees, and improper vaccination techniques. In most cases, nonsuppurative lymphadenitis regressed spontaneously, and suppurative lymphadenitis was drained spontaneously or by needle aspiration.