Immunization remains one of the most cost-effective public health interventions for reducing childhood morbidity and mortality. The aim of the study was to assess the immunization coverage and dropout rates among children aged 0–23 months attending a tertiary hospital in Otukpo, Benue State, Nigeria. A retrospective descriptive study reviewed routine immunization data extracted from the National Health Management Information System (NHMIS) register from January to December 2021 at the Federal University of Health Sciences Otukpo Teaching Hospital (FUHSO-TH). Data were collated and analyzed using descriptive statistics to determine frequencies, coverage percentages, and dropout rates. A total of 1,344 records were analyzed. The mean immunization coverage across all scheduled vaccines was 77.9%. The Bacillus Calmette-Guérin (BCG) vaccine had the highest coverage (87.9%), while the second dose of the Measles-Containing Vaccine (MCV2) had the lowest (65.4%). The highest dropout rate occurred between BCG and MCV1 (18.1%), followed by MCV1 and MCV2 (9.2%). The study concluded that, while early infant vaccine uptake is encouraging, overall immunization coverage remains suboptimal and falls short of the WHO 90% target. Strengthening community sensitization, defaulter tracking, and implementing reminder systems are essential to improve coverage, particularly for vaccines administered later in infancy.