How to Thicken Spaghetti Sauce: 7 Methods That Keep the Flavor

The fastest way to thicken spaghetti sauce is to simmer it uncovered in a wide pan for 20 to 45 minutes, stirring often, until the extra water cooks off. If you are short on time, a spoonful of tomato paste or a small cornstarch slurry will do the job in under 5 minutes. Both routes keep the tomato flavor bright instead of dulling it.

Thin sauce is a common complaint with any homemade spaghetti sauce. It is easy to fix once you know where the water came from.

Below are 7 ways to thicken spaghetti sauce, with exact amounts, timings and storage tips.

Why Your Spaghetti Sauce Is Thin

Runny sauce comes down to too much water and too little time to drive it off.

• Fresh tomatoes. Ripe tomatoes are roughly 94 to 95 percent water. A sauce made from fresh fruit needs a longer cook than one made from canned.
• A short simmer. Ten minutes warms the sauce but does not reduce it. Most tomato sauces need at least 20 to 30 minutes to lose noticeable volume.
• A lid on the pot. A covered pot traps steam. The water drips back in, so the sauce never thickens.
• Watery canned tomatoes. Some brands pack tomatoes in thin juice rather than puree.
• Wet pasta. Poorly drained pasta sheds water and leaves a pink puddle.

7 Ways to Thicken Spaghetti Sauce

Reduction and tomato paste build flavor. Starches and cheese mainly add body, so save them for quick rescues.

1. Simmer Uncovered to Reduce

Reduction is the classic fix. As water evaporates, the tomato sugars, acids and savory compounds concentrate.

1. Move the sauce to your widest pan. A 12-inch skillet exposes far more surface than a tall stockpot.
2. Hold a gentle simmer over medium-low heat. A hard boil splatters and scorches.
3. Leave the lid off. Stir every 5 minutes, scraping the bottom so the sugars do not burn.
4. Cook for 20 to 60 minutes, depending on how thin you started. Most batches of 4 to 6 cups thicken well in 30 to 45 minutes.

Season at the end, because salt concentrates as the sauce reduces.

2. Stir in Tomato Paste

Tomato paste is tomatoes already cooked down to a concentrate, so it adds body and deeper flavor at once. Use 1 to 2 tablespoons (about 16 to 32 g) for every 3 to 4 cups of sauce.

Fry it first in a teaspoon of olive oil for 1 to 2 minutes, until it darkens a shade and smells sweet. That browning removes the raw, tinny edge. Stir it in and simmer for 5 minutes.

3. Use Pasta Water and Finish the Pasta in the Sauce

This fixes the watery plate at the source. Pasta sheds starch into its cooking water, and that starch helps fat and liquid bind into a glossy coating.

1. Cook the spaghetti about 1 to 2 minutes short of the package time.
2. Scoop out 1 cup (240 ml) of the starchy cooking water before draining.
3. Add the pasta straight to the simmering sauce.
4. Toss over medium heat for 1 to 2 minutes, adding pasta water 2 tablespoons at a time, until the sauce clings to every strand.

The pasta soaks up liquid and releases more starch as it finishes. Cooking it in 2 quarts of water per pound makes the water even starchier. The same move makes vodka pasta silky rather than oily.

4. Add a Cornstarch Slurry

A slurry is the quickest true thickener. Cornstarch has roughly twice the thickening power of flour, has no taste of its own, and works in 1 to 2 minutes. Use 1 tablespoon cornstarch (about 8 g) mixed with 2 tablespoons cold water for every 2 to 3 cups of sauce.

Always mix cornstarch with cold water first; dry starch dropped into hot sauce forms lumps that will not dissolve. Pour the slurry in while stirring, then hold the sauce at a gentle simmer for 1 to 2 minutes. Starch granules start to swell around 140°F and finish thickening near the boil, so the sauce must bubble briefly to work fully.

Arrowroot alternative: arrowroot powder works the same way at about the same amount. It thickens at a lower heat, gives a clearer finish and holds up better in the freezer. It turns slimy with dairy, though, so skip it in cream sauces.

5. Make a Quick Roux With Butter and Flour

Flour thickens more gently than cornstarch and gives a soft, velvety body. Cooking it in fat first is the key, because raw flour tastes pasty.

Melt 1 tablespoon butter (14 g) in a small pan. Whisk in 1 tablespoon all-purpose flour (8 g) and cook, stirring, for 1 to 2 minutes until it smells nutty. Ladle in about 1/2 cup of hot sauce and whisk smooth, then stir that mixture back into the pot. This amount thickens 2 to 3 cups of sauce. Simmer for at least 5 minutes so the flour taste cooks out.

A roux suits meat sauces and is the base of many a creamy pasta sauce.

6. Stir in Grated Parmesan or Pecorino

Hard aged cheese thickens and seasons at once. Add 1/4 to 1/2 cup (about 20 to 40 g) of finely grated Parmesan or Pecorino Romano per 4 cups of sauce.

Take the pan off the heat first. Stir the cheese in a handful at a time. High heat makes cheese proteins clump and squeeze out fat, which leaves strings and an oily film. Cheese is salty, so taste before adding more salt. This trick also rescues a loose fettuccine Alfredo.

7. Blend in Vegetables or Add Breadcrumbs

Stir in 1/2 cup of mashed or blended cooked vegetables per 4 cups of sauce. Roasted red pepper, carrot, butternut squash and white beans all work. You can also use an immersion blender to puree a third of the sauce itself, which thickens it with no new ingredients.

Or add fine dry breadcrumbs: 2 tablespoons per 2 cups of sauce and simmer for 5 minutes. They soak up liquid and disappear into the sauce.

For cream-based sauces, a little extra heavy cream, simmered for 3 to 5 minutes, adds body. An egg yolk tempered with a ladle of warm sauce and stirred in off the heat also works.

Spaghetti Sauce Thickening Methods Compared

Common Thickening Mistakes to Avoid

• Too much starch. Adding a second and third slurry turns sauce gluey and dull. Add one dose, wait 2 minutes, then judge.
• Boiling cornstarch too long. Long, hard boiling and heavy stirring break the swollen starch granules, and the sauce thins out again. Simmer 1 to 2 minutes, then lower the heat.
• Raw flour taste. Flour stirred in dry, or not simmered long enough, tastes like paste. Cook it in fat first and simmer for at least 5 minutes.
• Scorching. Tomato sugars burn on the pan bottom. Keep the heat low and scrape as you stir.

How to Thicken Spaghetti Sauce in a Slow Cooker, Meat Sauce or Jar

Slow Cooker Sauce

Slow cookers trap moisture. Remove the lid for the last 1 to 2 hours on high, or prop it open with a wooden spoon. For a faster fix, stir in a cornstarch slurry and cook on high for 15 to 20 minutes, since slow cookers rarely reach a full boil.

Meat Sauce

Brown the meat well and drain excess fat before adding tomatoes. Tomato paste and a long uncovered simmer suit meat sauce best.

Jarred Sauce

Pour store-bought sauce into a wide skillet and simmer uncovered for 10 to 15 minutes. A tablespoon of fried tomato paste and a handful of Parmesan make it taste closer to scratch. You can find more ideas in our pasta recipes collection.

How Thick Should Spaghetti Sauce Be?

Good spaghetti sauce coats the back of a spoon and clings to pasta without pooling.

• Spoon test. Dip a spoon and run your finger across the back. The line should hold for a few seconds.
• Pan test. Drag a spoon across the bottom of the pan. The sauce should leave a clear trail that slowly closes.

Remember that sauce thickens as it cools and after it meets the pasta. Stop just before it looks perfect in the pot. Lighter sauces, such as pesto pasta, are meant to be looser and rely on pasta water instead.

Storing and Reheating Thickened Sauce

Refrigerate sauce within 2 hours of cooking, in shallow airtight containers. Under FoodSafety.gov guidance, cooked sauces with meat or vegetables keep for 3 to 4 days in the fridge. Frozen, they hold best quality for about 2 to 3 months.

Your thickening method matters for freezing. Sauces thickened by reduction, tomato paste or pureed vegetables freeze and thaw well. Cornstarch-thickened sauce freezes poorly: as it thaws, the starch can turn spongy and weep water. For freezing, thicken by reduction, or freeze it thin and add a slurry after reheating.

Reheat sauce to 165°F all the way through, loosening it with a splash of water if needed.

Thickening Spaghetti Sauce FAQs

The Best Way to Thicken Spaghetti Sauce

Start with an open pan and time, because reduction gives the best flavor. Add tomato paste for fast depth, and always finish the pasta in the sauce. Keep cornstarch, roux, cheese and vegetables for quick rescues.