The aim of the study was to obtain information about factors that contribute to the maternal competence of first-time mothers when the child is 3 months old. Data collection was by structured questionnaires. The sample consisted of 271 first-time mothers, who completed the questionnaires when their infants were 3 months old. The multivariate method used was a stepwise regression analysis. According to multivariate analysis, seven predictors remained in the model to explain maternal competence. The better the mother felt about succeeding in child care, the more balanced was her state of mind, and the more cheerful and easy-going the child was, the greater was the mother's competence. Younger mothers, those who received more concrete support from members of their social network and those who were more attached to their child showed better competence. Those mothers who received more guidance on breastfeeding from public health nurses also showed greater maternal competence. The research findings suggest that important factors that contribute to the maternal competence of first-time mothers include maternal resources, social support received from those close to the mother, and guidance on breastfeeding from public health nurses.