The Scheduled Tribes and Castes (STs and SCs) are the two most disadvantaged social groups in India. Previous studies have usually grouped the STs and SCs together as one disadvantaged group and have compared their educational and occupational mobility with the higher castes. We instead seek to compare health outcomes of the STs with not only the upper castes but also especially the SCs. We find that STs consistently perform poorly even relative to the SCs in terms of knowledge and usage of modern contraceptives, antenatal and postnatal healthcare, incidence of anemia and child immunization. However, female infant mortality is significantly higher among SCs than among STs, with no significant difference in male infant mortality between these groups. We find that ST women enjoy high social status and thus are unlikely to face impediments in accessing healthcare due to social norms that restrict women's autonomy. Oaxaca–Blinder decomposition methodology reveals that the health disparity between the STs and SCs for some key outcomes cannot be fully explained by differences in attributes between them. Suggestive evidence indicates that the health disparity can be likely attributed to the potentially greater marginalization that STs face even relative to SCs when accessing healthcare. This indicates the necessity to study STs in isolation from SCs so that policy can be designed to specifically target and mitigate health inequalities prevalent even among the most disadvantaged social groups.