Preheat your oven to 375°F (190°C).
Cook the spaghetti according to package instructions until al dente. Drain and set aside.
In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic, salt, and black pepper. Mix until well combined.
Form the mixture into meatballs, about 1 inch in diameter. You should have approximately 12-15 meatballs.
In a large skillet over medium heat, brown the meatballs on all sides, about 5-7 minutes. Remove from heat.
In a large baking dish, spread half of the marinara sauce on the bottom. Layer the cooked spaghetti on top, followed by the remaining marinara sauce.
Place the browned meatballs on top of the spaghetti and sauce. Sprinkle with Italian seasoning and top with mozzarella cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Let cool for a few minutes before serving.