Creamy Chicken and Spaghetti Squash Casserole

If you’re looking for a wholesome, comforting dinner that doesn’t feel heavy, this creamy chicken and spaghetti squash casserole is the perfect solution. Tender shredded chicken is baked together with roasted spaghetti squash and a creamy, flavorful sauce for a dish that’s satisfying, family-friendly, and surprisingly easy to make. It has all the cozy casserole vibes you love, but with a lighter twist that makes it perfect for weeknight dinners or meal prep.

Course Dinner

Keyword healthy, low carb

Prep Time 5

Cook Time 55

Total Time 1

Servings 4 servings

Equipment

9X9 Baking dish

Ingredients

1 Spaghetti Squash
Olive Oil
1/2 cup Sour Cream
3 tbsp. Pesto
1/4 cup Parmesan Cheese
3/4 cup Mozzarella Cheese
Salt, Pepper & Garlic Powder
1 cup Chopped Chicken
2 cup Cooked Spaghetti Squash

Instructions

Preheat your oven to 375°F. Carefully slice the spaghetti squash in half lengthwise and scoop out the seeds.
1 Spaghetti Squash
Drizzle the inside with olive oil and season with salt and pepper, then place the squash cut side down on a baking sheet.
Olive Oil, Salt, Pepper & Garlic Powder
Roast for 35–40 minutes, or until the flesh is tender and easily shreds with a fork. (This is also a great recipe to make if you already have leftover cooked spaghetti squash on hand.)
Once cooked, use a fork to scrape the squash into strands and measure out about 2 cups for the casserole.
Reduce the oven temperature to 350°F.
In a 9×9 baking dish, combine the sour cream, a spoonful of pesto, grated Parmesan cheese, shredded mozzarella cheese, salt, black pepper, and garlic powder, stirring until well mixed.
1/2 cup Sour Cream, 1 tbsp. Pesto, 1/4 cup Parmesan Cheese, 0.5 cup Mozzarella Cheese, Salt, Pepper & Garlic Powder
Add in chopped cooked chicken—leftover chicken or rotisserie chicken both work perfectly—along with the 2 cups of cooked spaghetti squash.
1 cup Chopped Chicken, 2 cup Cooked Spaghetti Squash
Stir everything together until evenly coated. Top with an extra sprinkle of mozzarella and a few dollops of pesto over the top.
2 tbsp. Pesto, 0.25 cup Mozzarella Cheese
Bake for about 25 minutes, or until the cheese is melted, bubbly, and lightly golden. Let it rest for a few minutes before serving.

Notes

Storage Tips For This Recipe

Fridge Storage

Store in an airtight container for up to 4 days.
If you can, let it cool completely before sealing so condensation doesn’t build up (that’s what makes squash watery).
If it’s super saucy/creamy, it actually reheats really well.

Freezer Option

Freeze in individual portions (makes life easier).
Store up to 2–3 months.
Thaw overnight in the fridge before reheating.

Heads up: spaghetti squash releases water when frozen, so after reheating you might want to drain off a little liquid or stir it well.

Reheating Tips (this matters)

Stovetop > microwave if you want the best texture. Add a splash of broth, milk, or cream while reheating to bring it back to life.
If microwaving, reheat in 30–45 second bursts and stir in between.
If it has cheese? A quick broil at the end = chef moment.

Common FAQ's Related to This Recipe

Can I use rotisserie chicken for this recipe?
- Yes! Rotisserie chicken works perfectly and makes this recipe even quicker. Just chop or shred it before mixing it into the casserole.
Do I need to salt the spaghetti squash before baking it?
- Yes, lightly salting it before roasting helps draw out moisture and enhances the flavor.
How do I know when spaghetti squash is done cooking?
- It’s ready when the flesh is fork-tender and easily shreds into spaghetti-like strands.
Can I make this recipe with leftover cooked spaghetti squash?
- Absolutely. If you already have cooked squash, this casserole comes together even faster.
Why is my spaghetti squash watery?
- Spaghetti squash naturally holds a lot of moisture. Roasting it cut-side down and letting it cool slightly before mixing helps reduce excess water.
Can I substitute Greek yogurt for sour cream?
- Yes, plain Greek yogurt is a great substitute and adds extra protein while keeping it creamy.
What type of pesto works best?
- Traditional basil pesto works beautifully, but sun-dried tomato pesto would also be delicious for a deeper flavor.
Can I use a different cheese?
- Definitely. Monterey Jack, provolone, or even a little sharp cheddar can work depending on your flavor preference.
Is this recipe low carb?
- Yes! Spaghetti squash is a lower-carb alternative to traditional pasta, making this a lighter option.
Can I make this ahead of time?
- Yes. Assemble the casserole, cover, and refrigerate up to 24 hours before baking. Add a few extra minutes to the bake time if cooking straight from the fridge.