This chapter provides a critical review of GIS-based multicriteria decision analysis (GIS-MCDA) for supporting group (collaborative and participatory) decision making. The review is based on a survey of referred papers that have been published over the last 15 years or so. The chapter offers a classification of the GIS-MCDA approaches for group decision making. First, the articles are classified according to the generic elements of the MCDA methods. Second, the GIS-MCDA methods are classified according to the various perspectives on collaborative decision support. These taxonomies of the GIS-MCDA approaches provide a background for an evaluation of the contribution of MCDA to GIS-based collaborative decision making.