Statement: A study to assess the effectiveness of self-instructional module on the knowledge of mothers regarding Acute Respiratory Infection in under five-year children in selected urban health centre in selected city. Objectives: To assess the effectiveness of Self Instructional Module on knowledge regarding ARI among mothers of under five year children and To find out the association of knowledge score with selected demographic variables. Methodology: Research Design used in this study is post-test only with control group design For present study sample size was 40 mothers of under five year children, simple random sampling technique was used for data collection. Result: Mean Knowledge Score Was Mean ± SD 13.75±1.07, where as in experimental group, the mean score 23.60±1.19(SD). The unpaired- t test value 27.56 shows significant difference between the control and experimental group knowledge scores and chi score test shows significant association between the post-test knowledge score with demographic variables.