The target of achieving exclusive breastfeeding for the first 6 months of life in Indonesia remains a challenge. Studies show a relationship between calorie intake of lactating mothers and success in 6 months of exclusive breastfeeding. This study aimed to compare the calories consumed between mothers who succeeded in 6 months of exclusive breastfeeding and those who did not and to investigate the effect of different types of supplementation. Methods: Three groups of lactating mothers (n=201) selected from cadres’ lists were followed for 6 months between June 2015 – July 2016. The first group was a control, the second group received milk (140 kcal/day), and the third group received milk and eggs (220 kcal/day). All food supplementation were given five days a week for as long as the mother was exclusively breastfeeding the infant. Cadres provided the mother supplements and ensured complete consumption. Each month, all groups were observed and measured on status of breastfeeding, anthropometry, and food consumption. Results: For all groups, calorie intake of those who succeeded in exclusive breastfeeding was significantly (p-value < 0.05) higher than those who failed. Calorie intake of lactating mothers is the most dominant factor (OR=5.6) for the success of 6 months of exclusive breastfeeding. The milk supplementation group had the highest calorie intake and highest percentage of mothers who were successful in providing 6 months of exclusive breastfeeding. Conclusion: Calories supplementation was found to be a significant factor in successfully achieving 6 months of exclusive breastfeeding. In this study, milk supplementation was more effective than milk and egg supplementation.