Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the cooked pasta with Alfredo sauce, salt, pepper, ranch dressing mix, shredded chicken, 1 cup of mozzarella, 1/2 cup of cheddar, and half of the chopped bacon. Mix until everything is evenly coated.
Transfer the pasta mixture into a 9x13-inch baking dish, spreading it evenly.
Top with the remaining cheddar and mozzarella cheeses, then sprinkle the remaining bacon pieces over the cheese.
Bake in the preheated oven for about 20 minutes, or until the cheese melts fully and the dish is hot and bubbling.
Serve immediately for the best flavor and texture.