Perinatal mental health difficulties can occur during pregnancy or after birth and mental illness is a leading cause of maternal death. It is therefore important to identify the barriers and facilitators to implementing and accessing perinatal mental health care. Our research objective was to develop a conceptual framework of barriers and facilitators to perinatal mental health care (defined as identification, assessment, care and treatment) to inform perinatal mental health services. Two systematic reviews were conducted to synthesise the evidence on: Review 1 barriers and facilitators to implementing perinatal mental health care; and Review 2 barriers to women accessing perinatal mental health care. Results were used to develop a conceptual framework which was then refined through consultations with stakeholders. Pre-planned searches were conducted on MEDLINE, EMBASE, PsychInfo and CINAHL. Review 2 also included Scopus and the Cochrane Database of Systematic Reviews. In Review 1, studies were included if they examined barriers or facilitators to implementing perinatal mental health care. In Review 2, systematic reviews were included if they examined barriers and facilitators to women seeking help, accessing help and engaging in perinatal mental health care; and they used systematic search strategies. Only qualitative papers were identified from the searches. Results were analysed using thematic synthesis and themes were mapped on to a theoretically informed multi-level model then grouped to reflect different stages of the care pathway. Review 1 included 46 studies. Most were carried out in higher income countries and evaluated as good quality with low risk of bias. Review 2 included 32 systematic reviews. Most were carried out in higher income countries and evaluated as having low confidence in the results. Barriers and facilitators to perinatal mental health care were identified at seven levels: Individual (e.g. beliefs about mental illness); Health professional (e.g. confidence addressing perinatal mental illness); Interpersonal (e.g. relationship between women and health professionals); Organisational (e.g. continuity of carer); Commissioner (e.g. referral pathways); Political (e.g. women's economic status); and Societal (e.g. stigma). These factors impacted on perinatal mental health care at different stages of the care pathway. Results from reviews were synthesised to develop two MATRIx conceptual frameworks of the (1) barriers and (2) facilitators to perinatal mental health care. These provide pictorial representations of 66 barriers and 39 facilitators that intersect across the care pathway and at different levels. In Review 1 only 10% of abstracts were double screened and 10% of included papers methodologically appraised by two reviewers. The majority of reviews included in Review 2 were evaluated as having low (n = 14) or critically low (n = 5) confidence in their results. Both reviews only included papers published in academic journals and written in English. The MATRIx frameworks highlight the complex interplay of individual and system level factors across different stages of the care pathway that influence women accessing perinatal mental health care and effective implementation of perinatal mental health services. These include using the conceptual frameworks to inform comprehensive, strategic and evidence-based approaches to perinatal mental health care; ensuring care is easy to access and flexible; providing culturally sensitive care; adequate funding of services; and quality training for health professionals with protected time to do it. Further research is needed to examine access to perinatal mental health care for specific groups, such as fathers, immigrants or those in lower income countries. This trial is registered as PROSPERO: (R1) CRD42019142854; (R2) CRD42020193107. This award was funded by the National Institute for Health and Care Research (NIHR) Health and Social Care Delivery Research programme (NIHR award ref: NIHR 128068) and is published in full in Health and Social Care Delivery Research; Vol. 12, No. 2. See the NIHR Funding and Awards website for further award information.