ABSTRACT The transition from the hospital is a vulnerable time for patients and stressful for caregivers?new treatments have been initiated, conditions require close monitoring, and the plan of care is in flux. Achieving a high-quality transition requires effective understanding of the discharge plan by patients/caregivers as well as seamless communication with key inpatient providers to address patients' concerns during and immediately after hospitalization. Use of patient portals in the acute care setting is a promising strategy to engage patient and caregivers during hospitalization, but is nascent at best. Furthermore, use of acute care patient portals during transition periods to activate patients in discharge preparation and to communicate directly with providers after leaving the hospital represents a novel use of health information technology (HIT). A web-based and mobile acute care patient portal that engages patients and caregivers during hospitalization has been designed, developed, and implemented as part of the PROSPECT project. A prototype of an interactive patient-centered discharge toolkit (PDTK) that is accessible from this portal has been previously developed, but has not yet been implemented or evaluated. The PDTK allows patients and/or caregivers to self-assess discharge preparedness via a validated, pre-discharge checklist tool and communicate directly with key members of the care team. As part of an AHRQ-funded Patient Safety Learning Laboratory (PSLL), the acute care patient portal has been integrated with Epic's electronic health record (EHR), and additional technical infrastructure is being developed and implemented. This includes a real-time patient-safety dashboard that can display the status of key safety threats including a discharge preparedness status indicator for unit-based clinicians, and a native mobile application that patients and caregivers can use during hospitalization and after discharge on personal devices. Thus, the infrastructure and clinical workflows necessary for patients, caregivers, and providers to access the PDTK will be available. A pilot and feasibility study will be conducted in which the PDTK will be implemented and evaluated on a general medicine unit that is a part of the PSLL project where patients and caregivers will be using the acute care patient portal. The RE-AIM (reach, effectiveness, adoption, implementation, and maintenance) framework will inform research questions and methods that guide implementation and evaluation. A pre-post study will be performed in which the primary outcome is analyzed as the proportion of patients with Patient Activation Measure (PAM) Levels 3 or 4 at discharge. Approximately 358 patients will be enrolled to provide adequate power to detect an improvement in the primary outcome from 72% to 84%. Quantitative and qualitative methods will be used to assess implementation, adoption, and use of the intervention. The results of this study will inform future efforts at other healthcare systems to adopt this or similar patient-facing tools integrated with vendor-based EHRs to promote self-management during transitions, as well as larger studies that are adequately powered to evaluate impact on post-discharge adverse events.