BackgroundIndia is experiencing a rising burden of chronic disease multimorbidity due to an aging population and epidemiological transition. Older adults residing in urban slums are especially vulnerable due to challenges in managing multimorbidity amid deprived living conditions. This study aimed to assess the prevalence of multimorbidity, associated health literacy, and quality of life impact in this population.MethodsA community-based cross-sectional study was conducted among 800 adults aged ≥ 65 years in an urban slum in Gujarat, India. Data on sociodemographics, physical and mental health conditions, health literacy (HLS-SF-47), quality of life (Short Form-12 scale), and social determinants of health were collected. Multimorbidity is ≥ 2 physical or mental health conditions in one person.ResultsThe prevalence of multimorbidity was 62.5% (500/800). Multimorbidity was significantly associated with lower physical component summary (PCS) and mental component summary (MCS) scores on the SF-12 (p < 0.001). After adjusting for sociodemographic variables, the odds ratio of 0.81 indicates that for every 1 unit increase in the health literacy score, the odds of having multimorbidity decrease by 19%. Older age within the older adult cohort (per year increase) was associated with greater odds of multimorbidity (AOR 1.05, 95% CI 1.02–1.09). Physical inactivity (AOR 1.68, 95% CI 1.027–2.77) and lack of social support (AOR 1.57, 95% CI 1.01–2.45) also increased the likelihood of multimorbidity.ConclusionThere is a substantial burden of multimorbidity among urban slum dwellers aged ≥ 65 years in India, strongly linked to modifiable risk factors like poor health literacy and social determinants of health. Targeted interventions are essential to alleviate this disproportionate burden among urban slum older adults.