In this work, an analytical model based on continuum mixture theories is developed to study the biaxial interfacial shear stresses in adhesive-bonded joints due to thermomechanical loading. The model predicts the effect of adhesive thickness and properties on the interfacial shear stresses. Two sets of governing partial differential equations are solved for the displacement field in each layer of the joint. The interfacial shear stresses between the adhesive and each adherend are determined using the constitutive equations. Numerical results show that both the adhesive thickness and the material properties have a significant effect on the thermomechanically induced interfacial shear stresses between the adherends and the adhesive. The proposed model inherently has the capacity for optimizing the selection of the adhesive thickness and material properties that would yield a more reliable bonded joint.