Researchers have found evidence that breastfeeding self-efficacy is an important variable that significantly influences initiation and duration rates. The purpose of this study was to develop a multi-factorial predictive model of breastfeeding self-efficacy in the first week postpartum. As part of a longitudinal study, a population-based sample of 522 breastfeeding mothers in a health region near Vancouver, British Columbia completed mailed questionnaires at 1-week postpartum. Bivariate correlations were used to select variables for the multiple regression analysis. The best-fit regression model revealed eight variables that explained 54% of the variance in Breastfeeding Self Efficacy Scale (BSES) scores at 1-week postpartum: maternal education, support from other women with children, type of delivery, satisfaction with labor pain relief, satisfaction with postpartum care, perceptions of breastfeeding progress, infant feeding method as planned, and maternal anxiety. The BSES may be used to identify risk factors, enabling health professionals to improve quality of care for new breastfeeding mothers.