Maternal mental health is a serious issue that affects both mothers and infants, necessitating increased knowledge and awareness among healthcare providers. This study assessed the effect of an educational intervention on maternity nurses’ knowledge and attitudes towards postpartum depression (PPD) using a quasi-experimental pre/post-one-group design. The sample consisted of 120 maternity nurses recruited conveniently from different maternity departments at the Ministry of National Guard hospital. The study used two valid and reliable instruments: The Postpartum Depression Literacy Scale (PODLIS) by Mirsalimi et al. (2020) and the Attitudes Scale adapted from Kang et al. (2019). The participants, predominantly aged 30-39 with at least a bachelor’s degree and holding SN1 nurse status, were mainly from Malaysia. The intervention significantly increased PPD knowledge in all domains, with the greatest improvement in risk factors and causes (10.09%). Positive associations existed between the pre-intervention attitude scale and professional help, recognition facilitation, and overall PPD knowledge (P < 0.05). Post-intervention, attitudes correlated positively with understanding risk factors and causes and facilitating recognition (P < 0.05). There were significant variations in the change of overall PPD knowledge based on the participants’ nationality (P < 0.05), and attending a PPD workshop significantly affected the change of attitude (P < 0.05). The study concluded the beneficial effects of the educational intervention on both knowledge and attitudes regarding PPD among maternity nurses. Customized educational programs are essential for preparing healthcare professionals with the necessary competencies and comprehension to deal with PPD effectively.