Background: Underweight is a prevalent condition among older adults in developing countries and poses a substantial burden on health, social, and aged-care systems. In this study, we examined the influence of tobacco use and food insecurity on the risk of being underweight among adults aged 60 or older in India. Methods: We used data from the 2017–2018 Longitudinal Aging Study in India. The sample size was 27,902 adults aged 60 years and above. We distinguished between smoking and smokeless tobacco use to examine how they may independently contribute to the outcome, while food insecurity was measured using the four-item version of the Food Insecurity Experience scale. Multivariable logistic regressions were conducted to assess the impact of tobacco use and food insecurity on the outcome. Additionally, we tested interactions between tobacco use and education, as well as between tobacco use and wealth. Results: The prevalence of underweight was 27% in the study population. Older adults who used smoking tobacco were twice more likely to be underweight than non-users (OR = 2.07, 95% CI = 1.79 to 2.40, p < 0.001), controlling for other confounders. The positive association between smokeless tobacco use and underweight was weaker but still significant (OR = 1.26, 95% CI = 1.11 to 1.42, p < 0.001). Food-insecure older adults were also more likely to be underweight (OR = 1.27, 95% CI = 1.10 to 1.48, p < 0.001). Other risk factors of underweight included males, rural residents, lower socioeconomic status (in terms of education, wealth, and caste), chewing disability, poor self-rated health, chronic lung disease, and tuberculosis. Interestingly, tobacco use moderated the relationship between wealth and underweight, such that smokers are more likely to be underweight as they become more affluent. Conclusions: Tobacco use and food insecurity have adverse implications on the nutritional status of the older persons in developing countries such as India. More targeted tobacco cessation measures and active food assistance programs for older adults are warranted to improve the overall health status of the older demographic.