This article experimentally examines axisymmetric adhesive contact under equi-biaxial stretch of the substrate. It is motivated by recent theoretical models which predict that the contact radius decreases sharply beyond a critical strain, with an instability that can result in spontaneous detachment or gross slipping across the contact area. The model system in the present experiments consists of convex glass lenses resting on poly(dimethyl siloxane) (PDMS) sheets, which are subjected to equibiaxial stretch in a specially designed experimental setup. It is shown that the evolution of the contact area is well described by the theoretical model after accounting for the mode-mixity dependence of work of adhesion at the contact edge. More significantly, the conditions of instability observed in the experiments were well predicted by the model. The findings are expected to be significant in predicting soft material contact behavior, such as that in biological adhesion.