This study aimed to examine the extent to which intellectual capital contributes to consolidating sustainable development concepts within civil society organizations in the southern governorates of Palestine. The study adopted both the descriptive analytical approach and a mixed-methods approach to integrate quantitative and qualitative evidence and provide a more comprehensive interpretation of the relationships among the study variables. Data were collected through a questionnaire administered to a sample of (250) employees working in civil society organizations, in addition to semi-structured interviews conducted with a purposive sample of (12) leaders and managers possessing relevant administrative and development experience. The collected data were analyzed using a set of advanced statistical techniques, including factor analysis, multiple regression analysis, and Structural Equation Modeling (SEM) through AMOS software, complemented by qualitative data analysis to provide deeper insights into the research findings,The results revealed a high level of intellectual capital within civil society organizations. Furthermore, relational capital emerged as one of the most prominent and influential dimensions, achieving an overall mean score of (3.92) with a standard deviation of (0.59), indicating the significant role of institutional relationships and external partnerships in enhancing organizations’ capacity to achieve their developmental objectives. The contribution of organizational relationships to attracting financial resources ranked first, with a mean score of (4.10), highlighting the strategic importance of institutional networks in strengthening financial sustainability and supporting the implementation of development programs and projects. Overall, the findings indicated that intellectual capital has a high level of contribution to advancing sustainable development practices, So The study concluded that intellectual capital represents a strategic cornerstone in consolidating sustainable development concepts within civil society organizations in the Gaza Strip governorates through enhancing organizational knowledge, improving resource management, and developing strategic relationships and partnerships. The study recommends adopting institutional policies that support the development of intellectual capital, increasing investment in human, structural, and relational capital, and strengthening communication mechanisms and strategic partnerships to improve institutional performance efficiency and maximize the developmental impact of civil society organizations in Palestine. Keywords: Intellectual Capital, Sustainable Development, Civil Society Organizations, Southern Governorates of Palestine