Cheesy Chicken Spaghetti Bake

This cheesy chicken spaghetti casserole brings together tender pasta, juicy chicken, and a rich, creamy sauce that transforms into the ultimate comfort food dinner. While it might look fancy enough for guests, it's straightforward enough for weeknight family dinners when you need something guaranteed to please everyone at the table.

I first created this recipe when looking for a way to elevate basic spaghetti night, and it quickly became my husband's most requested dish. The combination of two cheeses with the slight kick from the tomatoes and green chilies makes this dish impossible to resist.

Ingredients

• Thin spaghetti: creates the perfect base without overwhelming the sauce
• Boneless skinless chicken breasts: juicy and protein packed for a hearty meal
• Cream cheese: adds incredible creaminess and tanginess to the sauce
• Diced tomatoes & green chilies: provides the perfect balance of acidity and mild heat
• Cheddar and mozzarella cheese: creates that irresistible melty cheese pull
• Italian seasoning: a simple way to add herbal flavor without measuring multiple spices
• Butter and flour: the essential components for a perfect roux base
• Chicken broth: adds depth of flavor to the sauce beyond just creaminess

Step-by-Step Instructions

Prepare the Chicken:

Season chicken breasts with salt, pepper, and Italian seasoning before slicing them lengthwise. This doubles your surface area for seasoning and ensures quicker, more even cooking. Sear in hot olive oil until golden brown and just cooked through, about 5-6 minutes per side. The chicken will continue cooking slightly in the oven, so avoid overcooking at this stage.

Create the Sauce Base:

After removing the chicken, use the same pan to capture all those flavorful browned bits. Melt the butter over medium-low heat and add diced onions, cooking until they become translucent and start to soften. This slowly develops sweetness without burning. Add garlic just for the last minute to release its aroma without burning.

Make the Roux:

Sprinkle flour over the sautéed vegetables and stir constantly. This cooking process eliminates the raw flour taste and creates the thickening base for your sauce. The mixture will look paste-like and slightly golden. Cook for a full two minutes, stirring continuously to prevent scorching.

Develop the Sauce:

Gradually add chicken broth while whisking constantly to prevent lumps from forming. The sauce will initially thicken dramatically with each addition before thinning out. Once all broth is incorporated, slowly add the milk while continuing to whisk. Allow this mixture to simmer gently until it begins to thicken.

Incorporate the Cheese:

Add softened cream cheese in small portions, whisking until completely melted before adding more. This ensures a silky smooth sauce without lumps. Once fully incorporated, gradually add the shredded cheddar, stirring continuously until melted. The sauce should now be rich, creamy and coated the back of a spoon.

Combine Everything:

Fold in the drained tomatoes and green chilies along with the diced chicken. The acid from the tomatoes brightens the rich sauce while the chilies add just enough heat to be interesting without overwhelming. Mix in the cooked pasta, ensuring every strand is thoroughly coated in the creamy sauce.

Bake to Perfection:

Transfer everything to a baking dish if your pan isn't oven safe, and top generously with shredded mozzarella. Bake until the edges are bubbling and the cheese is melted. A quick broil at the end creates that irresistible golden brown top that everyone fights over.

Save

The cream cheese is truly the secret ingredient in this recipe. I discovered its magic when I was out of heavy cream one night and needed a substitute. The slight tanginess it adds completely transforms the dish from good to unforgettable, and now I wouldn't make it any other way.

Make-Ahead Instructions

This casserole is perfect for preparing in advance. Complete all steps up to the baking stage, cover tightly with foil, and refrigerate for up to 48 hours. When ready to serve, simply bake for an additional 10-15 minutes since you're starting with a cold dish. The flavors actually develop further as it sits, making this an excellent option for entertaining when you want to minimize day-of cooking.

Perfect Substitutions

If you're looking to customize this recipe based on what you have available, there are several easy swaps that work beautifully. Rotisserie chicken can replace the chicken breasts for an even quicker preparation. Any short pasta like penne or rotini can substitute for the spaghetti. For those who enjoy more heat, pepper jack cheese can replace some or all of the cheddar, or add a dash of cayenne to the sauce.

Serving Suggestions

This hearty casserole pairs perfectly with a simple green salad dressed with a bright vinaigrette to cut through the richness. Garlic bread is essential for sopping up every last bit of the delicious sauce. For a more substantial spread, roasted vegetables like broccoli or asparagus complement the creamy pasta beautifully while adding nutritional balance to the meal.

Recipe FAQs

→ Can I use rotisserie chicken instead of cooking chicken breasts?

Yes, absolutely! Using pre-cooked rotisserie chicken will save time and add great flavor. Simply shred or dice about 2 cups of rotisserie chicken and add it to the sauce when the recipe calls for adding the cooked chicken.

→ How can I make this dish ahead of time?

Prepare everything up until the baking step, then cover with foil and refrigerate for up to 24 hours. When ready to serve, remove from the refrigerator 30 minutes before baking, then bake at 400°F for about 20-25 minutes since it will be starting cold.

→ Can I freeze this chicken spaghetti casserole?

Yes, this dish freezes well! Prepare through the assembly stage, but don't bake. Cover tightly with foil and freeze for up to 3 months. Thaw overnight in the refrigerator before baking as directed, adding 10-15 extra minutes to the cooking time.

→ What can I substitute for the diced tomatoes and green chilies?

If you can't find diced tomatoes with green chilies, use regular diced tomatoes plus a 4 oz can of diced green chilies. For a milder version, use just diced tomatoes and add a diced bell pepper when cooking the onions.

→ Can I use a different pasta instead of spaghetti?

Absolutely! While spaghetti is traditional, this sauce works beautifully with penne, rotini, or farfalle. Just cook the pasta to al dente according to package directions, as different pasta shapes may have different cooking times.

→ How spicy is this dish?

This dish has a mild to medium heat level depending on the brand of diced tomatoes and green chilies used. The red pepper flakes garnish adds additional heat, so you can adjust or omit according to your preference. For a spicier version, add a diced jalapeño when cooking the onions.