Vulnerable migrant women are at an increased risk of developing postnatal depression, compared with the general population. Although some symptoms are the same as in other pregnant women, there are specific reasons why vulnerable migrant women may present differently, or may not recognise symptoms themselves. Factors associated with migration may affect a woman's mental health, particularly considering forced migration, where a woman may have faced violence or trauma, both in her home country and on the journey to the UK. Vulnerable migrant women engage less with maternity care than the average woman for reasons including a lack of knowledge of the UK healthcare system, fear of being charged for care, or fear that contact with clinicians will negatively affect their immigration status. This article explores the issues surrounding vulnerable migrant women that increase their risk of developing postnatal depression and presents reasons why this may go unrecognised by health professionals such as midwives.