Preheat your oven to 375 degrees F (190 degrees C).
This ensures it’s ready when you’ve mixed everything together.
In a large mixing bowl, combine the softened cream cheese, mayonnaise, sour cream, and ranch dressing.
Mix until the ingredients are well blended and smooth.
Add the thawed and drained spinach, garlic powder, salt, and half of the Parmesan cheese.
Stir everything together until the spinach is evenly distributed.
Transfer the mixture to an oven-safe dish and spread it evenly.
Sprinkle the top with the remaining Parmesan cheese and the shredded mozzarella cheese.
Bake in the preheated oven for 15 to 20 minutes until the dip is bubbly and the cheese topping is golden brown.
Remove from the oven and let it cool for a few minutes before serving.