This paper considers mobile bionanosensor networks designed for target tracking in molecular environments. The mobile bionanosensor network considered in this paper consists of nano-to-microscale bio-nanomachines that coordinate their activity by propagating the two types of signaling molecules: attractants for a group of bio-nanomachines to move toward targets, and repellents to spread over the environment. A mathematical model for target tracking is developed and the performance of mobile bionanosensor networks is defined based on distributions of targets and bio-nanomachines. Numerical results are then shown to facilitate discussion of the impact of attractants and repellents on target tracking performance.