The implementation of adult education in Ethiopia is the responsibility of different sectors. Studies indicated that the collaboration among these sectors is unsatisfactory, but the main factors that deter the collaboration are not well studied. Therefore, the purpose of this study was to assess major factors that deter intersectoral collaboration in the implementation of adult education in Ethiopia. The result revealed that low political commitment, lack of ownership and responsibility, lack of clear and feasible communication strategy, and lack of financial and skilled human resources are some of the major factors that impede effective intersectoral collaboration. The study implies that the presence of national strategy and preparedness of different sectors to collaborate are important but not sufficient condition to ensure effective intersectoral collaboration in the provision of adult education. It also implies that a program most likely fails when it is developed without genuine and meaningful consultation with its end-users. Generally, effective intersectoral collaboration requires political commitment, and greater synergy between policies and practices that considers the local context and active participation of the community.