This study determines the interrelationship between critical criteria affecting health, well-being, and productivity (WELL) in residential buildings within developing countries, using Malaysia as a case study. To achieve this, the objectives are to identify the relative criticality of health, well-being, and productivity in residential buildings, determine the critical criteria influencing these factors, and analyze the interrelationships among the identified critical criteria. Criteria were identified through semi-structured interviews and a Systematic Literature Review (SLR) of existing literature to develop the survey instrument. Survey responses were then gathered from 114 professionals residing in multi-story buildings. The data were analyzed using normalized mean analysis, the analytic hierarchy process (AHP), agreement analysis, and Spearman correlation analysis. From an initial list of 51 potential criteria, 20 were identified as critically impacting health, well-being, and productivity. These include: air filtration, ventilation design, air quality, property price, building structure, water management, water flow and supply, water treatment, pest management, thermal comfort/room temperature, parking (design and facilities), management services, waste management, mechanical and electrical services, recycling practices, garbage management, emergency evacuation plans, fire safety, sound barriers, and daylight/natural lighting design strategies. Notably, “water treatment” was highly correlated with both “water management” and “water flow and supply,” while “waste management” showed a strong correlation with “management services.” Similarly, “fire safety” was highly correlated to “emergency evacuation plans.” This study is the first to examine critical residential building criteria in a developing country context. Its findings offer comprehensive design insights for policymakers, enabling the development of holistic building assessment tools tailored to residential buildings.