Pre-stressing is becoming a most common and indispensable technique in the recent past for beams and girders in buildings and bridges. This paper presents the application of Finite Difference Method (FDM) for finding deflections in Pre-Stressed Concrete (PSC) beams with non-prismatic sections. Equations are derived for dead and live load bending moment, eccentricity, and depth at any required section. Based on these equations, it is initially established that conventional techniques cannot be adopted for finding deflections in pre-stressed concrete beams with non-prismatic cross-sections and hence FDM was adopted as an alternative. The calculated deflections using FDM are compared with those obtained from equivalent STAAD.Pro. Model and they found to be in close agreement.