While structural adhesives are used widely, relatively little is known regarding their plastic behavior. Few studies exist, for instance, to experimentally validate yield criteria for adhesives. The following considered adhesive joints under biaxial stress using an Arcan fixture. Adhesive strain was measured from the relative displacement of the adherends using digital image correlation. Two adhesive systems showed better correlation with a von Mises yield criterion in comparison to the commonly used Drucker-Prager criterion. The results were applied to a single lap shear joint, with mixed mode stress in the gauge section, which again showed better agreement with von Mises. The Drucker-Prager criterion, for instance, overestimated the yield stress by up to 11% while von Mises was within 2%.