Despite a campaign of effective educational interventions targeting knowledge, attitudes, and prevention, Human Immunodeficiency-Virus/Acquired Immune Deficiency Syndrome (HIV/AIDS) continues to be a significant public health issue in India, with Mizoram reporting the highest HIV/AIDS cases in 2018–2019. In this study, we extracted Mizoram state from the National Family Health Survey Fourth Series (NFHS-4) 2015–2016 datasets and investigated factors associated with respondents’ knowledge, attitudes, and prevention towards HIV/AIDS. The sample included 3555 adults aged 15–49 years residing in Mizoram, North-east India. Respondents who reported having ever heard of HIV/AIDS was 98%. Multivariate analysis indicated that the probability of having inadequate knowledge of HIV/AIDS was higher among those with no schooling, who were illiterate, of non-Christian faiths, belonging to backward tribes or caste, from poor households, and those who lived in rural areas, not exposed to media. The odds of mother-to-child transmission (PMTCT) of HIV/AIDS transmission was high among females (AOR = 3.12, 95% CI 2.34–4.16), respondents aged 35–39 years (AOR = 1.74, 95% CI 1.05–2.87) and those belonging to other backward class. The HIV/AIDS knowledge of respondents was found to be encouraging as the majority (98%) were considered to have a good level of understanding of the condition. An educational intervention to reduce the number of adults 15–49 years infected with HIV/AIDS in Mizoram should target those from low socioeconomic groups, those from non-Christian religions, and those from other backward classes.