Preheat your oven to 400°F (200°C) and grease a 2-quart baking dish.

In a large mixing bowl, combine the shredded chicken, basil pesto, mayonnaise, half of the shredded Parmesan cheese, and season with salt and pepper.

Transfer the chicken mixture into the prepared baking dish and spread it out evenly.

Scatter the halved cherry tomatoes and chopped mozzarella over the top of the chicken mixture, then sprinkle the remaining Parmesan cheese on top.

Place the dish in the preheated oven and bake for 20 to 22 minutes until golden brown.

Once baked, remove the casserole from the oven and let it cool for a few minutes before serving.