Abstarct: Slope stability in open-pit mines is a critical factor for ensuring safety and optimizing mining operations. The presence of groundwater and its associated pore water pressure significantly influence the mechanical behavior of rock masses, often reducing the slope safety factor. Traditional studies frequently examine these effects separately; however, this research aims to develop a comprehensive and accurate coupled hydro-mechanical model to assess groundwater flow and mechanical interactions on slope stability in the Midook copper mine. Using the finite difference software FLAC2D, numerical analyses were conducted on seven discrete slope sections to precisely simulate the complex interactions between pore pressure, permeability, and mechanical stresses. Four primary analysis cases were considered: dry conditions (no water presence), pore pressure effect without permeability, non-permeable undrained conditions, and a fully coupled hydro-mechanical model. Sensitivity analyses were also performed on key parameters, including pore water pressure and permeability, to quantify their influence on slope safety factors. The results indicate a significant reduction in the safety factor under fully coupled hydro-mechanical conditions, averaging up to 20% lower than the dry scenario. This decrease is attributed to the influence of pore water pressure and increased hydrostatic load, which reduce cohesion and internal friction angle, thereby diminishing the effective strength of the rock mass. Comparative evaluation of the coupled numerical model with conventional limit equilibrium methods (Slide) revealed that the coupled model provides more conservative estimates of critical slope conditions. On average, safety factors obtained from the limit equilibrium approach were about 18% higher than those from the coupled analysis, highlighting the risk of underestimating failure potential when ignoring coupled effects. Sensitivity studies confirmed that pore water pressure is the dominant factor affecting safety factor variability, while permeability controls fluid flow rates and thus the slope’s susceptibility to failure. These findings stress the necessity of incorporating coupled flow-stress modeling in the design of safe open-pit mine slopes. Furthermore, this study demonstrated that complex interactions between hydraulic pressures and hydro-mechanical parameters can locally and globally alter slope weaknesses and sensitivities. Numerical models capable of simulating coupled conditions better reflect real-world scenarios, advancing both technical understanding and practical applications for groundwater drainage system optimization and mitigation of sudden landslides. Finally, field investigations and analytical model results showed strong agreement, emphasizing the importance of aligning engineering methods with site-specific hydro-mechanical conditions in large-scale mining operations such as the Midook copper mine. The quantifiable reduction of safety factors by 15 to 20% under coupled conditions compared to dry scenarios underlines the critical risks of neglecting pore pressure effects, which can lead to erroneous decisions and potentially catastrophic failures.