One of the contributing factors in the growth and development of children under five is the mother’s ability to provide childcare, but young mothers do not have enough parenting skills. The goal of the current study was to examine the effect of the parenting peer education (PPE) programme on young mothers’ parenting self-efficacy and behaviour, and the growth and development of children under five. There were two groups, which were a control group (without intervention) and an intervention group, in which there were 15 participants in each group. Analysis covariance with the pre-test scores as covariates was used in this study. The results showed that, compared with the control group, the intervention group reported significantly better parenting self-efficacy, parenting behaviour, children’s growth, and children’s development, including cognitive, language, and motoric aspects. The PPE programme can exchange the young mothers’ experiences on how their children grow and develop, and the mothers will also receive psychological support. In conclusion, the PPE programme affected the young mothers’ parenting self-efficacy and parenting behaviour and the children’s growth and development.