In this paper, improved analytical models have been developed for more accurate determination of mode I and mode II compliances and strain energy release rates of adhesively bonded Double Cantilever Beam (DCB) type specimens. In these models, the effects of adhesive layer, elastic foundation and shearing deformation ahead of the crack tip due to the Saint-Venant end effect were considered. The improved analytical models were verified using finite element analysis (FEA), and excellent agreements were found for a variety of crack lengths. The comparisons of the measured and predicted testing machine loading point compliances with crack length at three different mixed-mode loading conditions for the adhesive layer thickness of 0.254 mm were also performed for further validation. In addition, contributions to the total mode I strain energy release rate from each effect are summarized.