Immunizations is one of the most successful and core effective public health investigation to bring healthy future generation. Though India had implemented the universal immunization schedule, the magnitude of its coverage is yet poor. The predominant reason for non-immunization is lack of knowledge and awareness among caretakers. Aim: The study aimed to assess the level of knowledge regarding immunization among mothers of under five children in OPD, Primary Health Centre, Abhishegapakkam, Puducherry. Methods: A descriptive design was utilized for the study. A sample of 75 mothers of underfive children were selected using convenient sampling technique. Result: The majority of mothers of under five children 40(53%) were found to have moderate knowledge, and 28(37.34%) of them had inadequate knowledge and only 7(9.34%) of them had adequate knowledge regarding immunization. However, there was no significant (P>0.05) relationship between age, education, religion, occupation, number of children to immunization. Conclusion: The study called for public oriented awareness programme on immunisation and its importance which helps to achieve the target.