Heat a large skillet over medium-high heat. Cook and stir sausage in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease.
Spread cream cheese in an even layer into the bottom of a 9-inch square baking dish. Layer salsa, sausage, and mozzarella over the cream cheese, respectively.
Bake in preheated oven until the mozzarella cheese is melted completely, about 20 minutes.