BackgroundFather–child interactions are associated with improved developmental outcomes among infants. However, to the best of our knowledge, no study has addressed the effects of paternal involvement on the neurodevelopment of infants who are less than 6 months of age, and no study has reported how maternal parenting stress mediates the relationship between paternal involvement and infant neurodevelopment during early infancy. This study investigates the direct and indirect relationship between paternal involvement and infant neurodevelopment at 3–4 months of age. The indirect relationship was assessed through the mediating factor of maternal parenting stress.MethodsThe participants were recruited through the Sesalmaul Research Center’s website from April to June 2014. The final data included 255 mothers and their healthy infants, who were aged 3–4 months. The mothers reported paternal involvement and maternal parenting stress by using Korean Parenting Alliance Inventory (K-PAI) and Parenting Stress Index (PSI), respectively. Experts visited the participants’ homes to observe infant neurodevelopment, and completed a developmental examination using Korean version of the Ages and Stages Questionnaire II (K-ASQ II). A hierarchical multiple regression analysis was used for data analysis.ResultsInfants’ mean ages were 106 days and girls accounted for 46.3%. The mean total scores (reference range) of the K-PAI, PSI, and the K-ASQ II were 55.5 (17–68), 45.8 (25–100), and 243.2 (0–300), respectively. Paternal involvement had a positive relationship with K-ASQ II scores (β = 0.29, p < 0.001) at 3–4 months of age, whereas maternal parenting stress was negatively related with K-ASQ II scores (β = −0.32, p < 0.001). Maternal parenting stress mediated the relationship between paternal involvement and early infant neurodevelopment (Z = 3.24, p < 0.001). A hierarchical multiple regression analysis showed that paternal involvement reduced maternal parenting stress (β = −0.25, p < 0.001), which led to positive infant outcomes (β = 0.23, p < 0.001).ConclusionsPaternal involvement is significantly associated with infant neurodevelopment during early infancy, and maternal parenting stress partially mediates that association. This result emphasizes the importance of fathers’ involvement and mothers’ parenting stress on early infant neurodevelopment.