To address the paucity of research investigating the implementation of multi-domain dementia prevention interventions, we implemented and evaluated a 24-week, bi-weekly multi-domain program for older adults at risk of cognitive impairment at neighborhood senior centres (SCs). It comprised dual-task exercises, cognitive training, and mobile application-based nutritional guidance. An RCT design informed by the Reach, Effectiveness, Adoption, Implementation, Maintenance framework was adopted. Outcome measures include cognition, quality of life, blood parameters, and physical performance. Implementation was evaluated through questionnaires administered to participants, implementers, SC managers, attendance lists, and observations. The program reached almost 50% of eligible participants, had an attrition rate of 22%, and was adopted by 8.7% of the SCs approached. It was implemented as intended; only the nutritional component was re-designed due to participants' unfamiliarity with the mobile application. While there were no between-group differences in cognition, quality of life, and blood parameters, quality of life reduced in the control group and physical function improved in the intervention group after 24 weeks. The program was well-received by participants and SCs. Our findings show that a multi-domain program for at-risk older adults has benefits and can be implemented through neighborhood SCs. Areas of improvement are discussed.Trial registration: ClinicalTrials.gov NCT04440969 retrospectively registered on 22 June 2020.