Common mental disorders (CMD) of depression and anxiety are prevalent and largely untreated among Kenyan pregnant and postpartum women living with HIV (PPWH). CMD lead to poor maternal and child health outcomes and contribute to lack of HIV care engagement and virologic failure in PPWH. While efficacious treatments for CMD exist, scaling treatment within routine health care in low- and middle-income (LMIC) settings will require stakeholder engagement and both effectiveness and implementation data to inform scale up and sustainability. Our team has integrated other efficacious interventions into antenatal (ANC) and HIV care in Kenya. We now propose to integrate proven mental health services using a collaborative care model, combined with a low intensity evidence-based intervention (problem solving therapy), while targeting known social determinants of HIV-related health for PPWH (stigma and IPV). Building on the current multidisciplinary approach for HIV care in Kenya, our proposed Collaborative Care Model (CCM) will utilize existing peer mentor mothers, non-specialist behavioral care managers, and psychiatric nurses; and will incorporate a consultant psychiatrist into the ANC/HIV care team. Guided by the EPIS (Exploration-Preparation-Implementation-Sustainment) framework, the overall study goal is to integrate collaborative care for perinatal CMD within routine ANC/HIV services in Kenya, assess the costs and cost-effectiveness of this approach, and work with policy and decision makers to determine key considerations for scale-up. Specifically, in Aim 1, we will identify contextual barriers and facilitators to refine an optimal integration model for delivering collaborative care model using multi- method data collection (focus groups with providers, in-depth interviews with key informants, and a clinic readiness checklist). A workshop with our Advisory Board comprising both county and national level stakeholders, will allow us to translate findings into a locally relevant CCM. In Aim 2 we will test CCM PPWH health during depression retention Aim 3, we will refine CCM implementation strategies through cost-effectiveness and dissemination research. We will carry out costing and cost-effectiveness analysis and invite policy and decision-makers to participate in a nominal group technique process to elucidate factors for further scale up and sustainment of the CCM approach. Findings from this study will developing a scalable model adaptable to other LMIC settings, contributing to global HIV and maternal health goals while and addressing the burden of untreated CMD. in antenatal care for in a hybrid type 2 implementation-effectiveness trial using a stepped wedge design at 15 primary care facilities in southwestern Kenya . We will i ntroduce CCM care for PPWH diagnosed with CMD antenatal care. The co-primary health outcomes at 12 months postpartum will be (1) recovery from or anxiety symptoms in PPWH, and (2) proportion PPWH with sustained viral suppre...