1-First Step: Get the pasta ready Start by bringing a large pot of water to a boil. Add enough kosher salt to make the water taste pleasantly seasoned, then cook the 1 pound dried spaghetti noodles until just al dente. This usually means a minute or two less than the package says. Drain the pasta well and set it aside while you make the sauce. Cooking the spaghetti a little firm matters because it will keep cooking in the oven. If the noodles are too soft at this stage, the final Alfredo Baked Spaghetti can turn mushy. If you are cooking for kids or picky eaters, this step still works well because the pasta finishes tender after baking.

2-Second Step: Make the creamy Alfredo base Set a large skillet or saucepan over medium heat and melt the 3 tablespoons unsalted butter. Once the butter is melted, whisk in the 3 tablespoons all-purpose flour. Cook this mixture for about 1 minute, stirring constantly, until it looks smooth and slightly bubbly. This gives the sauce a gentle cooked flavor and helps remove the raw flour taste. Slowly pour in the 3 cups whole or 2% milk while whisking. Add the 1 cup heavy cream and keep whisking until the mixture is smooth. Let it simmer for 4 to 5 minutes, stirring often, until it thickens enough to coat the back of a spoon. This is the base of your Alfredo Baked Spaghetti, so take your time here.

3-Third Step: Season and melt in the cheese Lower the heat a little and stir in the 1/2 teaspoon garlic powder and 1 teaspoon kosher salt. Then add about half of the shredded mozzarella and half of the grated Parmesan. Stir until the cheese melts into the sauce and the mixture looks creamy and glossy. If the sauce seems too thick, add a splash of the hot pasta water to loosen it. If it seems too thin, let it simmer for another minute or two. This is a good moment to taste and adjust the seasoning. Some cooks like a bit more salt, while others prefer the milder taste that lets the cheese shine.

4-Fourth Step: Combine the pasta and sauce Add the drained spaghetti to the sauce and toss until every strand is coated. A large spoon or tongs works well here. Keep mixing until the sauce clings evenly to the noodles and the pasta looks creamy from edge to edge. If you want to add cooked chicken, shrimp, broccoli, or another filling, fold it in now. This makes the Alfredo Baked Spaghetti more of a full meal and is handy for families who want protein built right into the casserole. You can also leave it plain for a simpler version that still tastes rich and satisfying.

5-Fifth Step: Assemble the baking dish Preheat your oven to 375°F. Lightly grease a baking dish, then spoon in the coated spaghetti. Spread it out so the top sits in an even layer. Sprinkle the remaining mozzarella and Parmesan over the pasta. This top layer gives the casserole that classic baked finish. The mozzarella melts into soft, stretchy pockets while the Parmesan adds a salty golden edge. If you like a little more browning, you can place the dish under the broiler for a short minute at the end, but watch it closely.

6-Final Step: Bake and serve Bake the Alfredo Baked Spaghetti for 20 to 25 minutes, or until the sauce is bubbling around the edges and the cheese is melted. Let it rest for about 10 minutes before serving. That short rest helps the sauce thicken so the portions hold together better. Finish with finely chopped parsley leaves if you want a fresh look and a light herbal note. Serve warm and enjoy it as a main dish for weeknight dinners, family gatherings, or a casual dinner party. This recipe is especially nice when you want something that feels homemade but still practical.