Assembly areas are first gathering places after earthquakes, and provide temporary sheltering. However if these areas have greater risks after earthquakes, they become more deadly. Current studies commonly look for evacuation shelter and temporary housing location models but most of them are not suited to assembly areas. This study aims to determine safe post-earthquake assembly areas by using the multi-criteria decision-making approach through an analytical hierarchy process using a geographical information system. 15 criteria were defined to evaluate the suitability in terms of spatial, natural structure and accessibility of each potential open space for emergency gathering. Following these criteria, possible areas were mapped, evaluated and scored with thematic hazard maps by using geographic information system in a case study to demonstrate the model. Finally, suitability layers were superimposed to estimate the safe assembly areas index and produce the city-scale infrastructure map. As a result, 107 assembly areas were designated for seven neighborhoods in Istanbul. Study results show that not every open area is safe to be a post-earthquake assembly area. The proposed method can provide useful information that could assist in earthquake disaster mitigation, and help government decisionmakers support further location allocation optimization of safe assembly areas.