Background: Exclusive Breastfeeding defined as the infant has to receive only breast milk from his/her mother with the exception of other kinds of food for six months. Exclusive Breastfeeding helps to prevent diseases to infants and it reduces risk of ovarian cancer to mother. Methodology: Descriptive cross sectional study was conducted among 124 lactating mothers with infants aged 6 months to one year attending Magomeni RCH Clinic in Kinondoni, Dar es Salaam. Simple random sampling procedure was used to obtain 124 lactating mothers. Data was collected from mothers who agreed to participate and signed the consent form by the use of close ended Swahili version questionnaire on assessing knowledge, practices and factors affecting Exclusive Breastfeeding among Lactating Mothers with Babies aged 6 months to 1 year attending Magomeni Reproductive and Child Health Clinic in Kinondoni district, Dar es Salaam.Result: About 74 (59.7%) respondents had high knowledge on EBF and 92 (74.2%) respondents initiated breastfeeding within one hour after delivery while 77 (62.1%) practiced exclusive breastfeeding. Findings show that 64(51.6%) respondents denied that exclusive breastfeeding causes loss of shape of their breasts while 48 (38.7%) respondents accepted that exclusive breastfeeding causes loss of shape of their breasts. Only 12 (9.7%) respondents didn’t know if EBF causes loss of breasts shape or not. Moreover, 19 (15.3%) respondents had physical difficulties/problems like cracking of nipples, inadequate milk, while 105(84.7%) didn’t get any physical difficult. Therefore there is significant association between mothers belief of losing shapes of their breasts and EBF (p=0.05). Physical difficulties/problems to lactating mothers study is significantly associated with EBF (p = 0.000).Conclusion: The overall knowledge among the lactating mothers with babies aged six months to one year was high and had good exclusive breast feeding practice. Although majority of the respondents are knowledgeable about EBF, the results show a gap between knowledge and actual practice within six months which is a recommended duration for Exclusive Breast feeding.