Although air pollution is a global problem, the densely populated developing countries, for instance, India, face severe air pollution. Rapid economic growth and poorly regulated developmental activities have further deteriorated the air quality in this region. Hence, a comprehensive investigation is essential to address the problems of air pollution in this region. In this study, we investigated the chemical composition and sources of PM₁₀ and PM_2.5 in 24 h particulate samples collected across seven urban sites (New Delhi, Kanpur, Prayagraj, Varanasi, Patna, Bhagalpur, and Kolkata) in Indo-Gangetic Plain of India during May–June 2017 in order to understand fate, sources and environmental effect of aerosols. Overall, the concentration of PM₁₀ and PM_2.5 (118–195 μg/m³ and 66–98 μg/m³, respectively) exceeded the National Ambient Air Quality Standard (100 μg/m³ and 60 μg/m³ for PM₁₀ and PM_2.5, respectively) set by the Central Pollution Control Board of India. The smaller cities (such as Bhagalpur and Varanasi) were relatively more polluted than some of the megacities (New Delhi and Kolkata). Carbonaceous aerosols (CAs) were more prevalent than water-soluble inorganic ions (WSIIs) irrespective of the particulate fraction. Generally, the NH₄⁺, Na⁺, and Mg²⁺ were mostly dominated in PM₁₀ and accounted for 35–67%, 1–17%, and 2–21% of WSIIs, respectively. While NH₄⁺, K⁺, and SO₄²⁻ were most abundant in PM_2.5, and accounted for 24–57%, 10–35%, and 8–15% of WSIIs, respectively. Organic carbon (OC) was 3–5 times higher than elemental carbon (EC) for PM₁₀ and PM_2.5 in every one of the seven sites. The source assessment study indicated that the large part of air quality in IGP is affected by local sources as well as long-range atmospheric transport of continental and marine air mass from south-west India, central India, and the Bay of Bengal.