The strategy applied in this study is fuzzy logic based decision-making system to achieve a rapid way to assess block-toppling failure instability in discontinuous rock slopes as justified by kinematic analysis that are applied to real cases. Referring to fuzzy logic based decision-making; the best option was selected from multiple fuzzy variables through performing a comparison and by obtaining the fastest solution for approximation. The expert system offers a capable fuzzy application for engineering judgment to be utilised in geotechnical decision making for engineering design. Kinematic analysis is currently used for the stability assessment of all types of toppling failures which provides the 'occurrence possibility' and is not capable of describing the stability conditions (degree of occurrences) in discontinuous rock slopes. Application of fuzzy logic complements kinematic analyses through giving a more accurate stability assessment. This study offers a complementary method for block-toppling failure instability assessment in discontinuous rock slopes based on artificial intelligence and a fuzzy expert decision-making system.