Background <p>Depression co-occurring with non-communicable diseases is a major public health concern among ageing population, particularly in low and middle-income countries like India. But, the complex hidden patterns, predictors and interrelationships among functional health, lifestyle behaviours and NCDs burden in shaping depressive symptoms remain insufficiently explored.</p> Methods <p>The present study utilized data from the Longitudinal Ageing Study in India Wave-1 (2017–2018), comprising 59,298 individuals aged 45 years and above. Exploratory and confirmatory factor analyses were conducted to derive latent constructs of functional limitations, lifestyle behaviours and NCDs burden. Structural equation modeling was used to examine direct and indirect associations with depressive symptoms and ordinal regression modeling was applied to assess important predictors of depression severity.</p> Results <p>Approximately 40% of participants reported some level of depressive symptoms. Three latent domains were identified, representing functional limitations, lifestyle behaviours and NCDs burden. The SEM showed acceptable fit (CFI = 0.923, RMSEA = 0.062). Functional limitations exhibited the strongest positive association with depressive symptoms (β = 2.052, <i>p</i> &lt; 0.001), followed by NCDs burden and lifestyle behaviours. Ordinal regression modeling results were consistent with functional impairment and poor self-rated health emerging as key predictors of higher depression severity.</p> Conclusion <p>The findings suggest that functional health plays a central role in the relationship between chronic disease burden, lifestyle factors and depressive symptoms. Interventions aimed at maintaining functional ability, alongside integrated management of NCDs and promotion of healthy behaviours, may help improve mental health outcomes among ageing population.</p>