Introduction: Childhood immunization is one of the most cost effective public health interventions to prevent vaccine-preventable diseases and improve child survival. In Nepal, the national immunization program aims to ensure that all children receive the recommended vaccines, yet challenges remain in achieving universal coverage. The Knowledge, Attitude, and Practice (KAP) of parents towards immunization play a critical role in vaccine uptake. This study was designed to assess their understanding, attitudes, and behaviors toward vaccinating their children. Methods: A prospective observational cross-sectional study was conducted from April 22, 2023, to October 2023 GP Koirala National Centre for Respiratory Diseases and Hospital, Tanahun, Gandaki Nepal, involving 227 parents of children under 18 months. The participants were selected through purposive sampling from Pediatric OPD of this hospital. A structured questionnaire was used to collect data about their knowledge, attitude, and practices regarding childhood immunization. The data were analyzed using SPSS version 23 with descriptive statistics, with results expressed as frequencies and percentages and Chi-square tests employed to identify associations between demographic variables and KAP levels. Results: The study revealed that 73.6% of parents had good knowledge about childhood immunization, recognizing the importance of vaccines and being aware of the vaccination schedule. However, only 64.3% of parents demonstrated a favorable attitude toward immunization, reflecting mixed perceptions about the necessity of vaccines and their safety. Additionally, 60.3% of parents exhibited good practices, indicating that while a majority ensured their children received vaccines, there were still gaps in adherence to the full immunization schedule. Demographic factor such as education level significantly influenced KAP scores. Conclusion: The study highlights the need for continuous efforts to enhance parental knowledge, improve attitudes, and reinforce good practices regarding childhood immunization in Nepal. Although the majority of parents showed a reasonable understanding of vaccines, the discrepancies in attitudes and practices suggest that targeted interventions, including education and outreach, are necessary to improve vaccination rates. Addressing these gaps is crucial to ensuring complete immunization coverage and safeguarding children from preventable diseases. Keywords: Childhood immunization, parental knowledge, vaccination practices, public health, vaccine uptake.