The rate of breastfeeding practice in general is high, but exclusive breastfeeding is not optimally practised as factors influencing it are multifaceted. As part of a cross-sectional survey using quantitative and qualitative approaches in DKI Jakarta Province between September and October 2005, this paper reports the risk factors of exclusive breastfeeding and potential roles of fathers in supporting exclusive breastfeeding practice. The subjects were mothers who have infants aged between 1.5 and 8.5 months. Data collected include exclusive breastfeeding practice, maternal characteristics, infant’s characteristics, family characteristics, exposure to various sources of information, and potential roles of fathers in providing emotional and physical supports for the mothers. Logistic regression was employed to identify determinants of exclusive breastfeeding practice. Coding of themes that emerged fromin-depth interviews was used to explain some phenomena found in the quantitative part of the study. Exclusive breastfeeding practice was 17.5%. Around 85% of the mothers ever experienced at least one lactation-related problem and had a 2.1 risk (95% CI: 1.1-3.8) of not practising exclusive breastfeeding. The lactation problems experienced may be mostly managed by non-medical professionals. As reported in the in-depth interviews, father’s roles included involvement during antenatal visits, in child caring and household works, as well as provision of comfort to the nursing mother when she is breastfeeding or feeling tired by massage. Although further confirmation is needed on the roles of Indonesian fathers to help manage lactation problems, the data from this study show that fathers do have the potential to do so.