Parasite are an integral part of virtually all food webs and species communities. Here we have considered a tri-trophic food chain model with disease circulating in the intermediate predator and there is an alternative food source of the intermediate predator. We have analyzed the local stability of the model system around the biologically feasible equilibria. We also introduce the ecological as well as the disease basic reproduction numbers and analyzed the community structure of the model systems by the help of these numbers. We have worked out theconditions of persistence of the model system. Our numerical results reveals that in low infection level the system shows chaotic dynamics but in high infection level chaotic dynamics becomes stable focus. So our finding contradicts predictions from previous models suggesting a destabilizing effect of parasites. We have also observed the role of alternative food on chaotic dynamics. When the alternative food increases the chaotic d