Increased competition for funding forces Humanitarian Organizations (HOs) into continuous improvement in their sustainable supply chain management processes, and to adopt innovative strategies, such as lean management, for efficient utilization of resources. Based on a synthesis of the literature on Lean Management, this study presents a model for assessing the readiness of such organizations for adopting lean management practices. This model was developed by identifying seven critical success factors (CSFs) for successful management of an HO’s processes. The model that was developed was validated by HO professionals by a questionnaire-based survey. Responses were collected from these HO professionals and the data analyzed by applying Partial Least Square Structured Equation Modeling (PLS-SEM). Results of the analysis provided a proved lean management readiness assessment model (LMRAM) which can be used for measuring the degree of an HO readiness for implementing a lean management system (LMS). The contribution of this framework is to improve the efficiency and sustainability (economic & social aspects) of an HO under scarce resource conditions through implementation of the LMS, without compromising the major objectives of the HO, which is the provision of relief to more target groups with the utilization of fewer resources.