ABSTRACT Arsenic-contaminated groundwater is a threat to the human population, leading to the occurrence of different cancers and skin problems. A health risk assessment study was conducted using arsenic data from groundwater sampled at Shahpur and Koilwar blocks in Bhojpur district, Bihar. The Inductively Coupled Plasma Mass Spectrophotometry (ICP-MS) analysis of 49 tube well samples (24 from Shahpur; 25 from Koilwar) showed that 22.45% of them had arsenic concentrations above the permissible limit (10 µg/l as recommended by the World Health Organization (WHO)) during the pre-monsoon with a maximum of 153 µg/l at Shahpur and 49 µg/l at Koilwar. The United States Environmental Protection Agency (USEPA) guidelines were applied to calculate the cancer and non-cancer risks. The Hazard quotient (HQ) and Incremental Lifetime Cancer Risk (ILCR) indicated an adverse risk (HQ > 1 and ILCR > 10−6), with Shahpur having three times higher amounts of more toxic arsenic(III). The Water Quality Index (WQI) obtained from chemical analysis indicated Shahpur having fewer poor water quality sites, with its percent ratio to Koilwar being 8:10. Ecological risk indices (Ei and RI) and Nemerow pollution index (NPI) implied moderate to extremely high risks (RI > 600 and 2.5 <NPI≤11). This study’s output necessitates future groundwater monitoring in the arsenic hotspots.