The study was aimed to assess the effectiveness of planned teaching programme on management of sibling rivalry among mothers of under five children and also to improve the knowledge of mothers regarding management of sibling rivalry. Objectives: 1) To assess the existing level of knowledge regarding sibling rivalry and its management among mothers of under-five children. 2) To evaluate the effectiveness of planned teaching programme on knowledge regarding sibling rivalry and its management among mothers of under-five children. 3) To find the association between post – test knowledge score with their selected demographic variables. Methodology: Pre- Experimental One Group Pre- test, Post- test only design was adopted in this study. 60 mothers of under five children were selected by using Non- Probability Convenient sampling technique, data was collected by using self- structured questionnaire on socio- demographic variables, knowledge on sibling rivalry and it’s management. Results: The study showed that 63% mothers have inadequate knowledge regarding management of sibling rivalry, 20% have moderately adequate knowledge, only 2% mothers have adequate knowledge in the pre- test. But in post- test 78% mothers have adequate knowledge, 20% have moderately adequate knowledge, only 2% mothers have inadequate knowledge, which was statistically significant at p- value is < 0.001. Conclusion: The study findings revealed that the planned teaching programme was effective, to bring out change in the knowledge regarding handling sibling rivalry.