Background: Groundwater arsenic contamination in the middle Indo-Gangetic plains is an emerging threat to human and livestock health. The present study was performed to determine the arsenic concentration in water and its residue level (bioaccumulation) in feed and the cattle reared in groundwater contaminated with Arsenic. A pilot study was executed to select the affected cattle of the contaminated (Test group) and uncontaminated zone (Control group) in Patna district. Based on the preliminary survey and study observations, ten cattle from the Akbapur village of Naubatpur block were selected as the control (C) group. Another ten cattle from Kasimchak village in Danapur block of Patna district, separated by 24 km were selected as the test (T) group. All selections were made to fulfil the inclusion criteria. Feed, water, and other biological samples such as blood, milk, hair, urine and dung were collected from each group. Samples were wet-digested, and As was analysed using an atomic absorption spectrophotometer (AAS) and a VGA generator. The mean level of As in the test group water (0.0785 ±0.004) and feed (1.046± 0.076) samples of Kashimchak village were above the WHO's permissible level and significantly higher than the As values in water and feed from the control group. The residue of As concentration in blood, milk, hair, urine and dung of test group were 0.286 ± 0.008, 0.08± 0.003, 1.692± 0.173, 0.083± 0.004, and 0.440± 0.011, respectively which was also significantly higher than control group (0.011± 0.003, 0.013 ± 0.006, 0.103 ± 0.0191, 0.032 ± 0.003, and 0.073 ± 0.009, respectively). The study thus indicates the bioaccumulation of As in cattle of contaminated areas, consequently impacting livestock's health and production. Government attention is required in the endemic districts of Bihar, which have geogenic contamination of arsenic in groundwater, to mitigate animal exposure for optimal production, good health, and welfare.