In this study, a comprehensive exergetic performance investigation of a single slope a passive solar still system is theoretically presented. Energy and exergy methodologies have been applied for all components of the solar still comprising glass cover, brackish water, and basin-liner. Also, exergy irreversibility analysis was conducted to identify and localize the sources responsible for the exergy destruction and losses in the system for further analysis and improvement. The theoretical model was solved numerically by using fourth-order Runge–Kutta method and the program was written by MATLAB. To examine the validity of the model, the numerical results were verified with the available experimental data in the literature. The numerical results were in good correspondence with the experimental data for the components’ temperatures and output productivity. The results showed that the maximum energy and exergy efficiencies of the proposed system are 32.5 % and 2.23 %, respectively. It is observed that the exergy efficiency has much lower value than the energy efficiency. The maximum irreversibility or exergy destruction in each component, i.e. glass cover, saline water, and basin-liner, has been estimated as 61.1, 50.2 and 717 W/m2, respectively, related to the maximum solar exergy input of 1005 W/m2. Furthermore, the results showed that exergy destructions rates in the solar still is proportional to the received solar insolation. From irreversibility analysis, it is found that the basin liner accounts for the highest exergy destruction (86% of the total exergy destruction).