Children's vaccinations play a significant role in public health efforts, particularly in reducing morbidity and mortality rates among children worldwide. However, challenges such as the accessibility of healthcare facilities, misinformation, and perceptions continue to affect the achievement of immunization goals in Tanzania and other developing countries. Based on the need to protect the community from diseases that can be prevented by vaccination, this study aimed to assess vaccination coverage and timeliness among children aged 12-23 months who attended postnatal immunization clinics in the Kongwa district located in the Dodoma region, Tanzania. A quantitative cross-sectional study was employed, involving 200 children who visited vaccination clinics along with their caregivers. Data were obtained through a questionnaire prepared and vaccination cards. This current study revealed that 96.0% were fully vaccinated, with 4.0% partially vaccinated, while no children were found to be totally unvaccinated. Timeliness varied across vaccines assed vaccines: 75.0% of Bacillus Calmette-Guérin vaccinated on time, four doses of Oral Polio Vaccine ranged from 74.0-87.0% of on time vaccination. Three doses of the Pentavalent Vaccine and Pneumococcal Conjugate Vaccine had on-time vaccination rates ranging from 79.5% to 86.0%. Two doses of the Rotavirus Vaccine reached on-time rates of 84.5% to 86.0%. 60.5% of people received the Measles and Rubella vaccine, with 35.5% experiencing delays and 4.0% remaining unvaccinated. This study revealed that, despite the national efforts to improve vaccination rates for children, issues such as delays and incomplete immunizations persist. Strategies like community engagement, continuous training for healthcare professionals, and improving healthcare accessibility in remote areas should be reinforced to improve vaccination uptake in Tanzania.