This study explores the structural behavior of pin-supported reinforced concrete (RC) deep beams under uniform loading using finite element analysis (FEA). The primary focus is on how flexural stress and deformation vary with different span-to-depth (L/D) ratios: 1.0, 1.278, 1.556, 1.833, and 2.083. Finite element models were developed in both two-dimensional (2D) and three-dimensional (3D) formats using ABAQUS software to evaluate stress distribution and deflection patterns across the beam’s depth. FEA was chosen for its ability to accurately model complex geometries, nonlinear material behavior, and support conditions areas where traditional analytical methods often fall short. The results show that as the L/D ratio increases, stress distribution trends become more linear, indicating a shift from deep beam behavior to that of conventional simply supported beams. Deflection differences between the top and bottom surfaces of the beam also reduce significantly, from 18.8% at L/D = 1 to 5.86% at L/D = 2.083. This suggests a more uniform deformation pattern as the span increases. The findings demonstrate the gradual behavioral transition of deep beams with increasing L/D ratios and highlight the critical role of computational tools like ABAQUS in structural analysis. This research offers valuable insights for improved design, analysis, and understanding of RC deep beams.