The Fifth International Conference on Algorithmic Decision Theory has been held on October 25 - 27, 2017 in Luxembourg and has been organized by Raymond Bisdorff (conference chair) and Jörg Rothe (program chair). The conference provided a multi-disciplinary forum to discuss algorithmic challenges of modern decision support system. The twenty-five papers covered topics such as preferences and multi-criteria decision aiding, decision making and voting, game theory and decision theory, and allocation and matching. Three invited talks provided interesting insights into novel paradigms for mechanism design, decision making in presence of the Internet of Things, and deceased organ matching. The conference furthermore included a poster session, an excellent banquet, and was preceded by a doctoral consortium. The conference proceedings have been published as Volume 10576 of the Lecture Notes in Artificial Intelligence series.