Background: Immunization is an attempt to generate immunity against a particular disease so that when exposed to disease, the body will not get sick or if sick only in mild conditions. This study aimed to determine the relationship between education level and time availability with the completeness of basic immunization during the COVID-19 pandemic in Sukoharjo Regency, Indonesia. Methods: This type of research is analytic observational with a sample of 100 mothers with children aged 0-20 months in Sukoharjo Regency. The research sample was collected through a non-probability sampling technique with quota sampling. Data were collected using questionnaires and MCH handbook in April?October 2021. Data analysis was carried out using the Chi-square test. Results: The research findings showed that the proportion of children who received complete basic immunization was 66%. The results of the bivariate analysis of basic immunization completeness with education level obtained p-value = 0.001 (p < 0.05) and time availability obtained p-value = 0.004 (p < 0.05). Conclusion: Based on the analysis results, it can be concluded that there is a relationship between the level of education and the availability of time with the completeness of basic immunization during the COVID-19 pandemic in Sukoharjo Regency.