Background Postnatal depression affects women from all cultures and countries. The postnatal period is thought to be a vulnerable time for all mothers. Immigrant women may be at particular risk as they attempt to adhere to childbirth rituals in western societies which might exacerbate stress, while navigating through the multiple stressors they face from migration in the transition to motherhood. Methods This study utilized a meta‐synthesis approach to synthesize qualitative studies exploring postnatal depression in immigrant mothers living in western countries. Searching six databases identified 16 studies that met criteria. Results The synthesis revealed two overarching themes of migration and cultural influences on immigrant mothers that interact and give rise to psychosocial understandings of postnatal depression, remedies and healthcare barriers. Mothers used self‐help coping strategies in line with this. Conclusions Immigrant mothers living in western countries are subject to multifactorial stressors following childbirth, increasing their susceptibility to postnatal depression. These stressors relate to being an immigrant in a western society and cultural influences, which may be harder to comply with, when removed from their sociocultural context. Social support appears to play a mediating role for these immigrant mothers. There were several similarities between immigrant and non‐immigrant mothers including their views of healthcare and medication, their health‐seeking behaviours and their fears of having their baby removed. All these findings have implications for healthcare settings in terms of assessments and service delivery. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message In this meta‐synthesis, we explored the experience of postnatal depression in immigrant women living in western countries, including the UK, the USA and Canada. Sixteen qualitative studies were reviewed, and their methodological quality was examined. The findings are based a total sample of 337 women. Two overarching themes were identified that are termed ‘cultural influences’ and ‘migration factors’, which influenced how these mothers coped with their postnatal depression. Social support played a mediating role for these immigrant mothers.