Back ground: The various child health programs were integrated in 1992 under the Child Survival and Safe Motherhood Program and have continued to be a part of the Reproductive & Child Health Programme implemented since 1997. Integrated Management of Neonatal & childhood illness (IMNCI) is a Child Health Intervention to be implemented as part of NRHM/RCH-II to bring down neonatal, infant & child mortality rate. During the mid-1990s, the World Health Organization (WHO), in collaboration with UNICEF and many other agencies, institutions and individuals, developed strategy known as the Integrated management of neonatal and childhood illness (IMNCI). Aim: To assess the knowledge regarding assessment and treatment of under five children based on IMNCI guidelines among staff nurses. Material and method: Study conducted by using the quantitative research approach by using descriptive research design was adopted to assess the knowledge regarding assessment and treatment of under five children based On IMNCI guidelines among staff nurses. Statistical Analysis Used: The collected data was organized, tabulated, analyzed and interpreted by using descriptive and inferential statistics based on the objectives of the study. Results and Conclusion: The study result shows that with regard to level of knowledge out of 30 staff nurses, 1(3.3%) had A+ grade, 1(3.3%) had A grade, 3(10%)had B+ grade, 14(46.7%) had B grade, 4(13.3%) had C grade, and (23.4%) had D grade.