Background Parenting sense of competence significantly affects the quality of parenting behaviours and healthy infant development. However, primiparous women without parenting experience may lack confidence and feel stress. This study aimed to explore the status of parenting sense of competence and identify its predictors among primiparous women. Methods A longitudinal study design was used. Primiparous women were recruited by using a convenience sample from two women's and children's hospitals in two cities in China. All primiparous women completed questionnaires on demographic characteristics, infant characteristics, family function, and parenting sense of competence at 1 month postpartum. At 3 months postpartum, each women's parenting sense of competence was re-assessed. Generalised linear regression was applied to identify the predictors of parenting sense of competence at 3 months postpartum. Results A total of 743 Chinese primiparous women were included in the analysis. The average parenting sense of competence score of the participants at 3 months postpartum was 70.18 (SD = 12.33). According to the generalised linear regression analysis, higher levels of parenting sense of competence at 3 months postpartum were significantly associated with older age (beta = 0.13, P = 0.005), better family function (beta = 0.37, P < 0.001), and higher levels of parenting sense of competence (beta = 0.35, P < 0.001) at 1 month postpartum. In contrast, lower levels of parenting sense of competence at 3 months postpartum were associated with poorer self-rated economic status (beta = - 0.16, P = 0.027), poorer infant health (beta = - 0.26, P = 0.007), and mixed or formula feeding (beta = - 0.11, P = 0.018) at 1 month postpartum. Conclusions Chinese primiparous women have a relatively good parenting sense of competence, but there is still room for improvement. Maternal age, economic status, family function, infant health, and feeding patterns were significant predictors. To improve their parenting sense of competence, more attention should be paid to primiparous women who are young, with poor economic status, having an unhealthy infant, and mixed or formula feeding. In addition, measures should also be taken during the early postpartum period to improve family function.