INTRODUCTION: Middle-aged adults with chronic conditions including diabetes, hyperlipidaemia and hypertension are at higher risk for cognitive decline. However, there is a lack of a targeted solution for this population. This study aims to develop a digital solution for salutogenic brain health targeting this population, assess its clinical effectiveness and evaluate the implementation in primary care settings by local champions, that is, nurses. METHODS AND ANALYSIS: A type-I hybrid effectiveness-implementation design with a sequential multiple-assignment randomised trial will be adopted. 160 adults aged 40-64 years old with chronic conditions hypertension, hyperlipidaemia and type-II diabetes will be recruited from three National University Polyclinics in Singapore. They will be randomised using block randomisation to either the intervention group ('Digital solution for Salutogenic Brain health' programme) or the waitlist control group. Cognitive tests, clinical measures, questionnaires and interviews will be used to evaluate outcome measures. The Reach, Effectiveness, Adoption, Implementation, Maintenance framework and the Capability, Opportunity, Motivation and Behaviour model will be employed to evaluate clinical effectiveness and implementation strategies. ETHICS AND DISSEMINATION: This study has been reviewed and approved by the National Healthcare Group Domain Specific Review Board (NHG DSRB) in Singapore (NHG DSRB Reference Number: 2023/00620 (25 June 2024)). Data will be analysed by study team members and findings will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT06582316.