Background: "Mother the most beautiful word on the lips of mankind" The post-partum period which can last up to 6 months after delivery. Changes during this phase are extremely gradual and pathology is rare. Several common problems that may arise during the breast feeding period, such as breast engorgement, plugged milk duct, breast infection and insufficient milk supply, originate from conditions that lead the mother to inadequately empty the breasts. WHO study shows that 60% of women between age 40 and 69 years come to the breast problems over 10 years periods Aims and objectives: The aim of the study is to assess the effectiveness of planned teaching programme on knowledge regarding selected breast related problems and their management among postnatal women at selected hospital, Vadodara. Material and method: The research design Pre-experimental-one group pre-test post-test design. The research approach is a Evaluative Approach with a view to assess the level of knowledge by pre-test on breast related problems among postnatal women. In the present study 40 postnatal women from selected hospitals were selected using Simple random sampling technique. Results: Mean percentage of pretest was 34.84 % with SD was 1.61 whereas, the mean knowledge of posttest was 18.98 and SD was 4.07 respectively. Further the effectiveness of mean knowledge was found to be 28.43 % from the pretest to posttest. The statistical pair T test was found to be 12.69*, that reflects significant effectiveness of knowledge score from pretest to posttest at P<0.05 significant level, revealing the effectiveness of planned teaching on selected breast problems. The knowledge of postnatal women regarding the selected breast related problems among the postnatal women's was poor before the administration of planned teaching. Conclusion: The planned teaching was effective in all knowledge aspect in posttest. So the hypothesis (RH1) is accepted and research hypothesis (RH2) is partially accepted.