Droughts repeatedly cause difficulties and losses to people in the Lam Ta Kong watershed. Proper drought mitigation and management strategies can effectively help prevent avoidable losses, and drought vulnerability assessment is the key to that. Consequently, this study aimed to assess the drought vulnerability of the Lam Ta Kong watershed with the involvement of the Analytical Hierarchy Process (AHP) and Geographical Information System (GIS) based on spatial analysis. The vulnerability assessment considered ten drought-influencing factors: slope, elevation, soil texture, soil fertility, stream density, precipitation, temperature, precipitation days, evaporation, and land use. The results demonstrated that most of the watershed, approximately 31.2% of the total area, was experiencing high vulnerability, 24.39% faced very high vulnerability, and 21.28% faced moderate vulnerability drought. The research pointed out that climatic factors were the critical factors influencing drought within the watershed, followed by geographical and anthropogenic factors. This also illustrates that mitigations and management plans should be developed, adapted, and designed considering these main factors and their spatial locations.