Abstract Background In recognition of the burden of Perinatal Mental Health problems, NHS England invested £365 million to transform women’s access to mental health care, including investment in Community Perinatal Mental Health Services. This study examined how elements of provider care affected women’s engagement with these services. Methods Semi-structured interviews were conducted with 139 women and explored their experiences of care from 10 different Community Perinatal Mental Health Teams; including which service components participants believed made a difference to their initial and continued engagement. Realist analysis was used to create context-mechanism-outcome configurations (CMOCs) across interviews, since not all parts of the configurations were always articulated within singular interviews. Results Four key pillars for engagement were identified: perinatal competence, relationship building, accurate reassurance, and reliability. The way perinatal competencies were relayed to women mattered; compassion, understanding and consistency were critical interactional styles. The extent to which these factors affected women’s engagement varied by their context and personal characteristics. Conclusions As mental health problems increase, disproportionately affecting vulnerable populations, it is critical to continue to ensure support is not only available, but appropriately meets the needs of those individuals. Our findings suggest that key staff behaviours applied at the right time can support women’s engagement and potentially contribute to better treatment outcomes.