This study aims to thoroughly assess the effectiveness of incorporating reinforcement in the form of soil nails to enhance the stability of a cohesive-frictional (c–ϕ) soil slope. The analysis employs two distinct methodologies—the limit equilibrium method (LEM) and the finite element method (FEM)—to ensure a comprehensive evaluation. A direct comparison between the results derived from limit equilibrium and finite element has been made. Additionally, an extensive parametric analysis has been conducted to examine the impact of several key parameters on slope stability, such as nail length and optimum spacing between them, nail reinforcement quantity (N), and the direction of nail placement. The results, along with corresponding failure patterns, are discussed in detail. Based on the findings, the study confirms the efficiency of soil reinforcement in enhancing the stability factor of natural c–ϕ slopes. Moreover, the influence of nail inclination and its optimal angle on the overall slope reliability has been highlighted. It was found that inclined nails provide greater resistance to deformation compared to horizontal nails, mainly when multiple nails are used. The influence of nail length and amplification factor on seismic resistance was minimal. The outcomes of this research would benefit geotechnical engineers aiming to improve the stability of existing slopes through soil nailing techniques.