Gather all ingredients. Preheat the oven to 350 degrees F (180 degrees C).
Fill a large pot with lightly salted water and bring to a rolling boil; stir in tortellini and return to a boil. Cook uncovered, stirring occasionally, until tortellini float to the top and the filling is hot, about 3 minutes. Drain.
Stir tortellini, prosciutto, pesto, and ½ cup mozzarella together in a large bowl.
Pour into a baking dish. Sprinkle remaining mozzarella over the top.
Bake in the preheated oven until cheese is melted and golden, about 10 minutes. Serve warm.
