A direct analytical beam formulation is developed for predicting the effective elastic stiffnesses and corresponding load deformation behavior of tailored box beams. Deformation of the beam is described by extension, bending, torsion, transverse shearing, and torsion related out-of-plane warping. The present analysis is developed without much dependence on thin-walled beam theory. Formulation of the analysis is in terms of a two-dimensional cross-section, instead of an infinitely thin contour enable stresses, strains, elastic properties to vary through the thickness of the beam walls in a manner consistent to the true laminated structure nature of the composite structure. This analytical model is very useful in studying non-classical phenomenon such as warping and in-plane elasticity. Governing differential equations for the extension, bending, torsion and shearing of the beam are derived using Newtonian approach. Validation studies are carried out for composite designs with no coupling, designs With varying degrees of extension-torsion and bending shear coupling, as well as • tdesigns with varying degrees of torsion-bending and extension shear coupling. The analysis is evaluated by correlation with existing experimental results.