Pregnancy is a significant event in a woman’s life and is associated with psychological and biological changes. Antenatal and postnatal care has traditionally neglects the emotional and psychological health and focuses on the physical health and consequently depression after pregnancy is overlooked and underdiagnosed. The study aims to identify the prevalence and the underlying determinants of Postpartum Depression (PPD) among newly delivered mothers. A cross-sectional study conducted in convenient sample of 52 PHCCs belonging to 13 health directorates (Kirkuk, Salahadin, Diyala, Anbar, Baghdad/ Karkh, Baghdad/ Rusafa, Babel, Karbala, Najaf, Wasit, Diwaniyah, Muthanna and Dhi Qar). The (1608) mothers within the first six weeks after giving birth who attended to PHCCs were included. Basic socio-demographic variables were compiled using a form that was filled through direct interview. PPD was assessed using Edinburg Postnatal Depression Scale with cutoff point ≥12. Data was collected during the period from October 1 to November 30 on 2019. The prevalence of PPD was 37.4%. The depressed mothers were significantly associated with; Age of mother and her husband, insufficient income family, neonatal complications, history of infertility, pregnancy complications, unplanned pregnancy, inadequate family care, family discord or domestic violence, history of depression or anxiety symptoms before or during pregnancy, and family history of mental disorders. The determinants of PPD were (inadequate family support, pregnancy complications, neonatal complications, family discord or domestic violence, psychological symptoms before or during the pregnancy and family history of mental disorders). PPD is a common illness and associated with many physical, social and psychological factors, it is not highlighted by society and health service providers, which requires spreading community awareness of the mental health concepts and increases the ability of health services provider to assess the mental health of pregnant mothers and manage mental disorders accompanying them.