The effects of mismatch parameters on isochromatic fringe patterns were studied using the technique of photoelasticity. First, the mathematical equations of isochromatic fringes were derived for singular stress field near a bi-material notch. These equations were used to study the effects of mismatch parameters on the shape of isochromatic fringes theoretically. Analytical results indicated that the mismatch parameters have a significant effect on the shape of the isochromatic fringe patterns around the bi-material notch tip. In order to assess the accuracy of the analytical results, a photoelastic test program was conducted on the V-notched bi-material Brazilian disc specimens. A very good agreement was shown to exist between the experimental results and the analytical reconstructions.