Background: Older adults (> 65 years) with multiple chronic conditions (MCC) and depressive symptoms experience frequent transitions between hospital and home. Care transitions for this population are often poorly coordinated and fragmented, resulting in increased readmission rates, adverse medical events, decreased patient satisfaction and safety, and increased caregiver burden. There is a dearth of evidence on best practices in the provision of transitional care for older adults with MCC and depressive symptoms transitioning from hospital-tohome. This paper presents a protocol for a two-armed, multi-site pragmatic effectiveness-implementation trial of Community Assets Supporting Transitions (CAST), an evidence-informed nurse-led six-month intervention that supports older adults with MCC and depressive symptoms transitioning from hospital-to-home. The Collaborative Intervention Planning Framework is being used to engage patients and other key stakeholders in the implementation and evaluation of the intervention and planning for intervention scale-up to other communities. Methods: Participants will be considered eligible if they are > 65 years, planned for discharged from hospital to the community in three Ontario locations, self-report at least two chronic conditions, and screen positive for depressive symptoms. A total of 216 eligible and consenting participants will be randomly assigned to the control (usual care) or intervention (CAST) arm. The intervention consists of tailored care delivery comprising in-home visits, telephone follow-up and system navigation support. The primary measure of effectiveness is mental health functioning of the older adult participant. Secondary outcomes include changes in physical functioning, depressive symptoms, anxiety,