Background: In late May 2012, Bagjan division of Borbam tea estate, of Sivasagar district of Assam was affected by an outbreak of acute watery diarrhea, subsequently confirmed as Vibrio cholerae O1. Objectives: Our objective is to investigate and control the acute diarrheal disease outbreak in Sivasagar district of Assam. Materials and Methods: A physician-epidemiologist-led team did rapid outbreak investigation to confirm the outbreak and instituted treatment and control measures. Quantitative data collection was done using standard schedule and qualitative data by using key informant interview schedule. Results: Spot mapping of cases was done along the garden residential lines. About 120 suspected cases were line listed; with 1:1.23 male: female ratio. Ages ranged from 3 to 70 years (median - 40.5 years). Attack rate was 4.79% with one death; case fatality rate was 0.83%. Open air defecation was practiced by 94.6%. Rectal swabs were positive for V. cholerae O1 (Ogawa). All the piped water samples were class IV unsatisfactory for domestic use. Conclusions: There is a need to improve water and sanitation facility in the tea garden lines along with implementation of a strengthened disease surveillance system through integrated disease surveillance project covering all tea estates.