Background – Exclusive breastfeeding in the first six months of life is cost effective and reduces the burden of infant morbidity and mortality. Sub optimal breast feeding especially nonexclusive breast feeding in the first six months of life results in 1.4million deaths and 10%of disease burden in children’s. (Ayisi and Wakoli, et al 2014) Objective – To assess the pattern of breast feeding and its effect on occurrence of diarrhea among mothers of less than six months’ infants among kirkos sub city, Addis Ababa, Ethiopia Methodology- Institutional cross sectional study was conducted from –February 1st to March 30 on a sample of 450 participants were included in the study. Data were collected using pre-tested structured questionnaire. The data were cleaned, coded, entered in to SPSS version 20 and analyzed. Results:The prevalence of exclusive breast feeding in the study population found 68.2%and partially breast feed was found 31.8%.the prevalence of diarrhea among exclusively breast feed children found 7.6%while among partial breast feed10.4%with in the previous 2 weeks to the study time. The odds of occurrence of diarrhea among children who exclusively breast feeding were found 0.254 times lower than those partially breast feed, AOR 0.254(0.154,0.419) and p value 0.000 at 0.05 level of significance. Conclusion According to this study Exclusive breast feeding up to 6months have protective effect for diarrhea disease.