This Pesto Spaghetti Squash is a cozy, low carb dinner that tastes like pasta night: roasted spaghetti squash strands tossed with tender chicken and bright basil pesto, then baked under a bubbly layer of mozzarella and parmesan. It's filling, family-friendly, and comes in at about 12 grams of net carbs per serving.
The first time I cooked spaghetti squash, I was curious and a little skeptical. Could a squash really stand in for a big bowl of pasta? One cheesy, garlicky bite later, I was sold. Spaghetti squash isn't just a pasta substitute. With a good pesto and a golden cheese topping, it's a dish that stands on its own, and nobody at the table feels like they're missing out.
Key Ingredients & Substitutions
The Pesto: Store-Bought vs. Homemade
Pesto is where most of the flavor in this dish comes from, so it's worth a minute of thought. Homemade pesto is the version in the recipe card below: fresh basil, toasted pine nuts, parmesan, garlic, a pinch of red pepper flakes and good olive oil, blitzed in a food processor in about five minutes. It's brighter and greener than anything from a jar, and you control exactly what goes in it, which matters when you're counting carbs. Basil, nuts, cheese and oil are all naturally low carb, so homemade pesto adds very little to the total.
Store-bought pesto is a perfectly good shortcut on a busy weeknight. Use about ¾ cup in place of the homemade batch. A shelf-stable jar like Barilla pesto is handy to keep in the pantry, and the refrigerated tubs near the deli counter taste a little fresher. Either way, read the label: some brands bulk up the sauce with potato flakes, sugar or cheaper oils. Look for basil, oil, cheese and nuts near the top of the ingredient list, and check the carbs per serving before you buy.
- Spaghetti squash. Pick one that feels heavy for its size, with firm, even yellow skin and no soft spots or cracks. A large squash (about 3 pounds, which gives you roughly 6 cups of cooked strands) feeds four as a main dish. If yours is on the small side, add a little extra chicken to keep the dish filling.
- Cooked chicken. Rotisserie chicken is the easy route, but leftover grilled or baked chicken works just as well. Shred it or cut it into bite-size pieces so it mixes evenly through the squash.
- Mozzarella and parmesan. Mozzarella gives you that stretchy, melty top, while parmesan brings the salty, nutty flavor and browns beautifully. Fontina or Gruyère are tasty swaps if you want to switch things up.
- Olive oil. A little goes on the squash before roasting, and the rest goes into the pesto. Use a good extra virgin olive oil for the pesto since you'll really taste it. Our guide to olive oil explains what to look for.
Helpful Tips
Roast it cut side down. Placing the squash halves face down on a foil-lined sheet lets them steam and roast at the same time, so the strands come out tender instead of dry. Start checking at 45 minutes: a butter knife should slide through the skin easily. Undercooked squash is crunchy and hard to shred, and overcooked squash turns mushy, so it's worth checking.
Drain away extra moisture. Spaghetti squash holds a lot of water. After you scrape out the strands, let them sit in a colander for a few minutes or gently press them with paper towels. This keeps the finished bake creamy instead of watery, and it helps the pesto cling to every strand.
Toast the pine nuts gently. Pine nuts go from golden to burnt in seconds, so stay by the pan and shake it often. Toasting brings out a buttery, rich flavor that makes homemade pesto taste restaurant-worthy. Let them cool before blending so they don't turn the basil dark.
Stream in the oil. Pulse everything else in a food processor first, then drizzle the olive oil in while it runs. That creates a smooth, emulsified pesto rather than an oily one. Taste and adjust the garlic, salt or red pepper flakes before you mix it in.
Use a small baking dish. An 8x8-inch dish like this Emile Henry square baker keeps the layer deep enough to stay saucy underneath while the cheese browns on top. In a bigger pan the squash spreads thin and can dry out.
Variations
- Chicken, your way. The recipe already uses cooked chicken, but you can make it your own: try grilled chicken thighs for more flavor (our Grilled Caesar Chicken Thighs are great chopped up in here), or crisp up some bacon and add it with the chicken.
- Pesto shrimp. Swap the chicken for about ¾ pound of shrimp. Sauté them in a little olive oil and garlic for 2 to 3 minutes, just until pink, then fold them in before baking. If you love shrimp, try our Keto Garlic Butter Shrimp too.
- Sun-dried tomato. Stir in ⅓ cup of chopped sun-dried tomatoes in oil for sweet, tangy pops of flavor. They add a few carbs, so keep the amount modest. Our Low Carb Pasta Alfredo with Sun-Dried Tomatoes is another way to enjoy them.
- Extra veggies. Mix in a couple of handfuls of baby spinach, sautéed mushrooms or roasted zucchini for more volume without many carbs.
- Different pesto. Try our Spinach Pesto or Low Carb Lemon Balm Pesto for a fresh twist.
- Nut-free. Use sunflower seeds in place of the pine nuts, or leave the nuts out and add a little extra parmesan.
Serving Ideas
With chicken, squash and cheese all in one dish, this is a complete meal on its own. For an Italian-style dinner, add a crisp green salad with our Low Carb Italian Dressing and a few slices of almost-zero-carb garlic bread for mopping up the pesto.
It also pairs nicely with roasted broccoli, green beans or asparagus. If you're feeding a crowd, serve it next to a Low Carb Chicken Caesar Salad and let everyone build their own plate.
Storing & Freezing
Store leftovers in an airtight container in the refrigerator for 3 to 4 days. Reheat individual portions in the microwave for 1 to 2 minutes, or warm the whole dish, covered with foil, in a 350°F oven for about 15 minutes. It makes an easy grab-and-go lunch.
You can freeze it, but the texture changes a little. Spaghetti squash releases water as it thaws, so the bake comes out softer and wetter. If you want to try, freeze portions in airtight containers for up to 2 months, thaw overnight in the fridge, drain off any liquid, and reheat in the oven so the extra moisture cooks off. For the best results, freeze the homemade pesto on its own in an ice cube tray, then roast fresh squash when you're ready to cook.
FAQs
Is spaghetti squash keto?
Spaghetti squash fits a keto or low carb diet in sensible portions. A cup of cooked spaghetti squash has roughly 7 to 8 grams of net carbs, compared with about 40 grams in a cup of regular cooked pasta. It's not as low as zucchini noodles, so if you're keeping strictly to 20 grams of carbs a day, watch your portion size and fill out the plate with protein and cheese, the way this recipe does.
How many net carbs are in this pesto spaghetti squash?
Made as written with homemade pesto and divided into 4 hearty servings, each serving has about 12 grams of net carbs (around 15 grams of carbs minus 3 grams of fiber). That makes it a solid low carb dinner. If you need it lower, cut it into 6 servings for about 8 grams of net carbs each and add a side salad, or add extra chicken so a smaller scoop of squash still fills you up. Store-bought pesto can change the numbers slightly, so check your jar's label.
More Low Carb Spaghetti Squash Recipes
If you love this Pesto Spaghetti Squash, here are a few more spaghetti squash recipes to try:
- Garlic Butter Spaghetti Squash
- Low Carb Spaghetti Squash Casserole
- Spaghetti Squash Arrabbiata
- Spaghetti Squash Au Gratin
- Spaghetti Squash Fritters
📖 Recipe
Pesto Spaghetti Squash
Ingredients
Equipment
Step-by-Step Instructions
- Preheat the oven to 400°F (200°C) and line a rimmed baking sheet with foil.
- Slice the spaghetti squash in half lengthwise and scoop out the seeds. Rub the 1 tablespoon of olive oil over the cut sides, then season with salt and pepper.
- Place the halves cut side down on the baking sheet and roast for 45 to 50 minutes, until a butter knife slides easily through the skin. Let cool for about 10 minutes, until you can handle them.
- While the squash roasts, make the pesto. Toast the pine nuts in a dry skillet over medium-low heat for 3 to 5 minutes, shaking the pan often, until lightly golden. Let them cool for 10 minutes.
- Add the toasted pine nuts, basil, ¼ cup parmesan, garlic, salt and red pepper flakes to a food processor and pulse until roughly chopped.
- With the processor running, slowly stream in the ¼ cup olive oil until the pesto is smooth. Taste and adjust the salt or pepper flakes.
- Use a fork to scrape the squash into strands and transfer them to a large bowl. If there's liquid pooling, drain the strands in a colander for a few minutes or blot with paper towels.
- Add the chicken and pesto to the squash and toss until everything is evenly coated.
- Spread the mixture in an 8x8-inch baking dish and top with the mozzarella and ½ cup parmesan.
- Return to the oven and bake for 15 to 20 minutes, until the cheese is melted, bubbling and golden in spots. Let cool for 5 minutes before serving.
Nutrition
Notes
Tried this recipe?
Let us know how it was!Nutritional information is provided as a courtesy and is my best approximation. Net carbs are calculated as the total grams carbs minus the total grams of fiber.
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