Social justice in the distribution of water and wastewater services means that access to safe water sources and sanitary wastewater disposal systems, as a fundamental right, should not be affected by the economic or geographical situation of citizens. Ultimately, achieving this justice is not the only solution to reducing urban inequalities, but is also a vital prerequisite for promoting public health, environmental sustainability, and preventing health crises in the entire urban fabric. The purpose of the present study is to assess social justice in the distribution of water and wastewater services in different urban areas, case study: Tehran metropolis. The MABAC method was used in this study. This study is applied-theoretical in terms of purpose and descriptive-analytical in terms of method. The required information and data were collected through library and field methods. With the aim of measuring the level of access to regions and identifying infrastructure gaps, this study uses the MABAC (Multi-Attractive Comparative Assessment) multi-criteria decision-making model to analyze and rank the 22 regions of Tehran. This method, by utilizing various technical, economic, and social indicators, calculates the distance of each region from the threshold, and depicts the true state of spatial justice in the urban service network. The findings of this study, in addition to accurately identifying underserved areas and explaining the extent of inequality, provide an efficient platform for policymakers to take an operational step towards realizing spatial justice and sustainable urban development by intelligently prioritizing resource allocation and infrastructure renovation.