The purpose of this study was to adapt a strategic management model for use in not-for-profit organisations in Namibia. Such organisations are facing increasingly turbulent environments and strategic management has been useful for allowing them to adapt better and to remain sustainable. Not-for-profit organisations, also known as the third sector, make a significant economic contribution; a contribution which, in Namibia, amounted to 2.1% of GDP in 2015/16. However, not-for-profit organisations are largely reliant on donor funding. In Namibia, such funding has declined by 33% since 2010, accounting for just 6% of total health expenditure in 2014/15. A triangular approach to strategic management, with a strategic focus on financial sustainability, programme sustainability and people sustainability, is deemed to be the most effective way to address sustainability in not-for-profit organisations. Accordingly, a qualitative study was undertaken to investigate the way in which not-for-profit organisations that receive PEPFAR funding and operate in the field of HIV/AIDS in Namibia conduct their strategic management. A pragmatic research philosophy was followed with an abductive approach to theory development. The research strategy comprised a case study conducted within a cross-sectional time frame. Purposive sampling was used to identify the 12 research participants, with whom semi-structured interviews were conducted. Data were subsequently analysed using content and thematic analysis. The study concluded that not-for-profit organisations in Namibia carry out limited strategic management. The thematic analysis, however, showed relationships between strategic management and sustainability, strategic management and financial sustainability, strategic management and programme sustainability, and strategic management and people sustainability. A strategic management model was subsequently adapted for use in not-for-profit organisations in Namibia. This model covers the stages of strategic management, namely, the business mission, external and internal analyses, strategy formulation, programme formulation, implementation, as well as feedback and control. Additionally, the model addresses strategic management and the triangular sustainability of organisations in terms of financial, programme and people aspects, and presents the tools necessary for both external and internal analysis during strategy making. This study concludes that the use of this adapted model for strategic management will contribute to the sustainability of not-for-profit organisations in Namibia. / Business Management / D. Phil. (Management Sciences)