Joint tracking and classification (JTC) is rapidly gaining momentum recently. Algorithms have been proposed for this problem. However, performance of tracking and classification has been evaluated separately without considering their interdependence. In this paper, we propose a joint measure, named joint probability score (JPS), to account for tracking error, misclassification and their interdependence. The basic idea of JPS is to measure the difference between the cumulative distribution functions (CDFs) of the ideal JTC and the one to be evaluated. Moreover, performance of tracking and classification can be unified by applying CDF. The proposed method is unit free and positive definite. Also, it has close connections with stochastic dominance and the so-called continuous ranked probability score. Two examples illustrating our JPS are presented. The results demonstrate that JPS reflects well the joint performance of tracking and classification.