[SUMMARY] Aim: The “Nursing Guidelines for Childrearing Support in Older Primiparas in the First Month Postpartum (NGCSOP)” targeted older primiparous women to help them physically and psychosocially adapt to childrearing. This study aimed to evaluate the effectiveness of multiple interventions based on nursing guidelines implemented in hospital-based postpartum care for older primiparas during the postpartum period. Methods: A pre-post quasi-experimental design was employed. The nursing guidelines comprised a set of 35 recommendations for postpartum care settings that were implemented in four hospitals in Japan. Primiparous women aged ≧35 years were enrolled in the control group before implementation of the guidelines (n = 91) or in the intervention group after implementation of the guidelines (n = 108). Outcomes were assessed using questionnaires for fatigue, depressive symptoms, maternal confidence, and maternal satisfaction at early postpartum and at 1 month and 2 months postpartum. Results: At 1 month postpartum, the proportion of women with an Edinburgh Postnatal Depression Scale score of ≧9 in the intervention group was significantly lower than that in the control group [χ2(1) = 5.75,p = .019]. No significant differences were found between the two groups in fatigue, maternal confidence, and satisfaction during 2 months postpartum. Conclusions: Implementation of the NGCSOP in hospital-based postpartum care contributed to a significant reduction in postpartum depressive symptoms at 1 month postpartum in the intervention group. Further studies are needed to improve the guidelines by making them more effective and feasible in clinical care settings.