Introduction: Anthrax is a neglected zoonotic disease worldwide. In Odisha, outbreaks have been reported annually since 2009, with four hotspot districts – Koraput, Sundergarh, Rayagada, and Deogarh. While supporting the response efforts at the district level, an undetected cluster of acute diarrhoeal disease (ADD) was identified at one of the blocks and was investigated for gastrointestinal anthrax with the objective of confirming the outbreak and identifying risk factors.Methods We defined a probable human anthrax case as acute painless cutaneous lesions or acute fever, gastrointestinal illness, regional lymphadenopathy, and contact with dead livestock within 7 days of onset in a Sakiaguda resident during 15 March–22 May 2023. A laboratory-confirmed case was a probable case with Bacillus anthracis detected by RT-PCR in blood or stool. We did a 1:2 unmatched case-control study with asymptomatic neighbourhood controls. We calculate adjusted odds ratios (aOR) with 95% CI. We collected data on livestock anthrax vaccination from the district animal husbandry department.Results We identified 38 cases (median age and IQR in years 38 [20–50]; 60% females, 100% from indigenous tribe), of these, two were laboratory confirmed, with zero case fatality. Among cases, 97% (37/38) had gastrointestinal manifestations and 3% (1/38) had cutaneous manifestation. Among 38 cases and 76 controls, we identified that consumption of dead livestock meat (AOR: 51.88; 95% CI: 11.5–234) was significantly associated with case status. For the affected village, the routine anthrax vaccination coverage in livestock for 2021 was 50% (314/633); it was missed in 2022. Following the confirmation of human anthrax cases, ring vaccination of the livestock with 54% (314/633) coverage was done in 2023.Conclusion This was a confirmed human gastrointestinal anthrax outbreak associated with the consumption of dead livestock meat. There were gaps in routine anthrax vaccination for livestock and in reporting of sudden livestock deaths. We recommended health education with behaviour change communication for dead livestock disposal practices, and strengthening anthrax vaccination programme for livestock.