Reinforced concrete beams are important structural elements that transmit the loads from slabs to columns. They can be classified into three types depending on the span to depth ratio as deep beam, slender beam and very slender beam. Slender reinforced concrete beams are those where the breadth of the compression face is small compared with its depth. The deflection of these members results from two main components, namely the bending or flexural deflection and the shear deflection. Shear span to depth ratio of these members is greater than 2.5. They transfer shear by combination of stress in the transverse reinforcement, if provided (also called steel contribution) and stress in cracked and uncracked concrete section (commonly referred to as concrete contribution). In this study, general purpose nonlinear finite element analysis (FEA) program ABAQUS software was used to study the deflection behavior of slender beams having shear span to depth ratio of 3.0 to 5.0. The FEA accounts for material nonlinearity for both steel and concrete. The finite element modeling was validated by comparing the result obtained from Finite Element Analysis to result from experimental result done previously by another researcher. The mean values needed for simulating the finite element model was derived from the mean compressive strength of concrete. In a parametric study, longitudinal reinforcement grade, transverse reinforcement grade, concrete grade and cross sectional depth has been studied. The load-deflection relationship is used to study the effect of each parameter. In general the load-deflection behavior of nonlinear finite element analysis model shows good agreement with the load-deflection behavior from the experimental result. Using increased quality of stated parameters results in improved load carrying capacity of slender RC beam members.