The behavior of composite material is a result of integrated contribution of fiber, matrix, and fiber/matrix interface. Applied load to members must effectively get transferred from matrix to fibers via interface. It is extremely important to study and understand the nature of the interface of any given composite system. The flexural behavior of wood filled steel tubes is largely dependent on interactions at wood/steel interface.The objective of this paper is to present the work carried out to study the behavior and determine the interfacial shear stress in wood filled steel tubes. Interfacial shear stress is studied considering simple mechanical bonding by interference fit and adhesive bonding by structural epoxy adhesive.The experimental results obtained indicate that the interfacial shearing strength is higher in the case of adhesively bonded wood/steel interface. And also the moment capacity of rectangular wood filled steel tubes of adhesively bonded wood/steel interface is higher. This also proves that flexural behavior of wood filled steel tubes is largely dependent on interfacial shear strength. It is also observed that the adhesively bonded beams fail in tensile at the bottom face incase of short beams having span-to-depth ratio about 6.9 and long beams having span-to-depth ratio about 13.6 fail in compression at top face with v-shape on both side webs.