The bronzing disease of Thai jackfruit (Artocarpus heterophyllus Lam.) has recently appeared in Vietnam, causing a significant loss for farmers, but its control method is still restricted. In this study, we identified pathogens based on morphological and molecular characterizations. A total of 25 bacterial isolates were isolated from diseased samples. The bacterium produces white or yellow pigment in culture, is gram-negative, slightly pleomorphic, non-motile, facultatively anaerobic, short-rod, and catalase-positive. It hydrolyzes gelatin and starch but not tween 80, and produces acid from glucose, sucrose, and lactose. The bacterium does not produce indole and does not produce hypersensitivity to tobacco. The results of sequencing of the encoded region of synthesis of capsular polysaccharide (cpsD) and pathogenicity-related genes HrpS confirmed that the causative agent is Pantoea stewartii subsp. stewartii. The pathogen’s possible host range could be traditional jackfruit varieties, fruits, and crops such as durian, longan, mango, tomatoes, broccoli, pumpkin, cucumber, corn, rice, sweet potatoes, water spinach, peanuts, and green beans. The P. stewartii subsp. stewartii could enter the host plant cell through open wounds or natural openings such as stomata. The results confirmed the presence of P. stewartii subsp. stewartii in Vietnam and suggest that the jackfruit tree should not be planted in plantations with these crops to prevent cross-contamination and the spread of pathogens.