IntroductionThe Package of Essential Noncommunicable Disease Interventions—Plus (PEN-Plus) is a strategy decentralising care for severe non-communicable diseases (NCDs) including type 1 diabetes, rheumatic heart disease and sickle cell disease, to increase access to care. In the PEN-Plus model, mid-level clinicians in intermediary facilities in low and lower middle income countries are trained to provide integrated care for conditions where services traditionally were only available at tertiary referral facilities. For the upcoming phase of activities, 18 first-level hospitals in 9 countries and 1 state in India were selected for PEN-Plus expansion and will treat a variety of severe NCDs. Over 3 years, the countries and state are expected to: (1) establish PEN-Plus clinics in one or two district hospitals, (2) support these clinics to mature into training sites in preparation for national or state-level scale-up, and (3) work with the national or state-level stakeholders to describe, measure and advocate for PEN-Plus to support development of a national operational plan for scale-up.Methods and analysisGuided by Proctor outcomes for implementation research, we are conducting a mixed-method evaluation consisting of 10 components to understand outcomes in clinical implementation, training and policy development. Data will be collected through a mix of quantitative surveys, routine reporting, routine clinical data and qualitative interviews.Ethics and disseminationThis protocol has been considered exempt or covered by central and local institutional review boards. Findings will be disseminated throughout the project’s course, including through quarterly M&E discussions, semiannual formative assessments, dashboard mapping of progress, quarterly newsletters, regular feedback loops with national stakeholders and publication in peer-reviewed journals.