Leachate is a noxious liquid with a high concentration of organic and inorganic substances produced by interactions of several environmental factors in a landfill. It is quite toxic to groundwater, surface water, and the environment; thus, it must be treated thoroughly before disposal. There are a few traditional and advanced technologies that exist for the treatment of landfill leachate, which are broadly categorized as biological, physicochemical, and hybrid technologies. According to the literature, every technology has pros and cons, and no single treatment method is sufficient to provide the required efficiency. Thus, selecting the optimal methodology for landfill leachate treatment requires a multi-criteria decision-making (MCDM) approach that incorporates several criteria and alternatives. In the research, integrated AHP-TOPSIS and integrated Fuzzy-TOPSIS approaches were employed to evaluate their potential to rank the available treatment options and to determine the optimal treatment strategy for optimal treatment of leachate. In this decision-making process, ten criteria (the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen, and heavy metals, operation and maintenance cost, installation time, treatment time, environmental effect, simplicity of operation and maintenance, and treatment plant flexibility with dependability) were considered. The weights of the considered criteria were determined using the AHP and Fuzzy techniques. A combination of two biological techniques, a combination of physical and biological methods, and an integration of the physicochemical method with biological methods were included among the considered alternatives (treatment approaches). The alternatives were prioritised with the help of integrated decision-making processes from a total of fifteen different treatment options. The findings indicate that membrane biological reactor (MBR) (A8), advanced oxidation process (AOPs) + MBR (A10), and coagulation-flocculation (A13) and up-flow anaerobic sludge blanket reactor (UASB) + Membrane filtration (MF) (A1) (A8>A10>A13>A1) are the first four treatment approaches as determined by only AHP, integrated AHP-TOPSIS, and Fuzzy-TOPSIS methodology. The calculated results indicate that the hybrid methods are better suited than conventional treatment approaches for toxic landfill leachate treatment.