Lifestyle modification, including dietary interventions, physical activity, and stress management, has proven crucial in the non-pharmacological management of cardiometabolic risk factors. However, the efficacy of these interventions in the context of cardiometabolic multimorbidity (CMM) within the unique demographic and cultural milieu of India is inadequately explored, despite Indians exhibiting distinct susceptibility to cardiovascular diseases. This study aims to address existing knowledge gaps by assessing the effectiveness of a culturally tailored lifestyle toolkit based on the WHO-HEARTS framework in improving health outcomes among individuals with CMM and exploring the intergenerational preventive dimension. The study adopts a two-arm non-blinded Cluster Randomised Controlled Trial design to include adults diagnosed with CMM, defined by the presence of diabetes mellitus, stroke, or heart disease, aged 18 years and above, providing informed consent, and agreeing to follow-up. The trial spans three cohorts in Ernakulam (Kerala), Tigiria (Odisha), and Sheragada (Odisha), encompassing a total population of 330,055. The intervention, a ’lifestyle toolkit,’ integrates guidance on diet, physical activity, stress management, tobacco and alcohol cessation, and drug adherence. It leverages community health volunteers and an M-health platform for implementation. The comparator is Standard of Care (SoC), involving patient-initiated physician visits. Primary outcomes include changes in glycaemic control (HbA1c), while secondary outcomes encompass changes in blood pressure, body mass index, quality of life scores, diet patterns, stress levels, tobacco and alcohol usage, drug adherence, and physical activity. Measurements involve point-of-care devices and digital tools. The study duration is 36 months, with a sample size of 2000 participants distributed across 40 clusters. Statistical analysis includes repeated-measures ANOVA and multilevel models, employing an intention-to-treat approach. The study’s novelty lies in its holistic approach, addressing various facets of CMM comprehensively.