Interface failure pertinent to composite sandwich T-joints with high shear strength core under tensile and bending loads is investigated. Experimental studies performed on composite T-joints, under the action of tension and bending, indicate interface failure as the dominant mechanism. Subsequent finite element analysis reveals that critical location of failure initiation is localized in the corner of web-adhesive interface, based on maximum principal stress criterion. However, a good correlation between the failure load prediction from finite element analysis and that from the experimental measurement is not obtained. This is because the finite element modelling does not take into account the presence of imperfections due to spacer mesh, voids formation, poor adhesive filling and neglects any fixture misalignment. Further, analytical expressions for the peel stress at the interface are obtained using strength of materials approach. The critical peel stress is higher than numerical simulation value due to further redistribution of peel stress by the presence of adhesive fillet and thin adhesive layer, and linear strain variation approximation used in the analytical model. The presented peel stress analysis can also be construed as a conservative tool for design purposes.