Introduction Immunisation is one of the key public health instruments to combat childhood morbidity and mortality. However, the lack of mothers' knowledge and motivation to vaccinate their children has affected vaccination programs and vaccination coverage rate in the state of Jharkhand. Therefore, addressing this knowledge gap, our study aims to evaluate the extent of mothers' understanding of the effects and aspects of vaccination for their children. Materials and method This is a cross-sectional study conductedat the paediatric vaccination clinic of Rajendra Institute of Medical Sciences (RIMS), Ranchi between October 2022 and September 2023. The sample population included 200 mothers as participants (18 years and above). The survey was done with a self-administered questionnaire of questions about socio-demographic factors, mothers' knowledge, and mothers' practices, and answers were consolidated in the form of a table. Results The majority of participants in this study were below 25 years of age and were literate. The missed vaccination percentage was also significantly higher among illiterates, mothers below 30 years of age, and unemployed ones. Among the respondents, 73.3% of illiterate mothers, 56% of those below 30 years of age, and 64% of unemployed mothers missed their children's vaccination schedule. Among the mothers, 75% did not know the names of vaccine-preventable diseases. Of the respondents, 50% believed intercurrent illnesses like fever and the common cold to be side effects and contraindications of vaccines. Among the mothers, 65% never posed any questions to the paediatrician. Of the mothers, 97% safely kept the vaccination card and 82% relied on government or public health centres for vaccination purposes. Conclusion The majority of our population was in favour of vaccinating their children but there existed a huge lacuna in their knowledge about vaccination. This study concludes that firmer measures have to be exercised to bridge this knowledge gap. Only this can improve the vaccination coverage rate.