How to Thicken Spaghetti Sauce – 9 Simple Ways

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Last updated on May 11, 2021

Homemade spaghetti sauce should be in every home cook’s repertoire. When the luscious sauce you’re aiming for turns out feeble and watery, there are so many ways to muscle it up, and you'll be sure to have at least one remedy in your kitchen! Keep reading for a thorough guide of the best ways to thicken spaghetti sauce. 


Technique 1 - Add a Starch

Starches are long chains of glucose molecules that are used by plants to store energy. Under heat, they gelatinize, soaking up excess water in the solution. Below are some common starch thickeners.

1) Cornstarch Slurry

This technique involves a 1:1 ratio of cornstarch and water, mixed until smooth. Add this slurry to the sauce 1 tsp at a time, stirring it in well and then waiting for one minute, until you reach a consistency you like.

Powdered cornmeal can also be used if you have a food processor/blender

Ingredients Needed: Cornstarch and water

Tools Needed: bowl, whisk or fork


  • Has no Effect on Appearance of Sauce


  • Easy to Over-Do it

Suggestions: Cornstarch thickens quickly, but not immediately, so give it a little time to work before you add more.

2) Use Pasta Water (from traditional wheat pasta)

As you boil pasta, it releases much of its starch into the surrounding water. A few spoonfuls of water from cooked (or nearly cooked) pasta added to your sauce will contribute the starch you need to thicken it.

Ingredients and Tools Needed: Everything you're already using.


  • Requires no extra ingredients or tools


  • Won't work for gluten free pasta

Suggestions: Your sauce will get a bit thinner at first (you just added water), but then it will begin to thicken as you cook your sauce a minute or two longer.

3) Use Mashed Potatoes (GLUTEN FREE)

It sounds crazy, but potatoes are basically pure starch and have extraordinary thickening power. Use leftovers, or microwave a single peeled potato until it is very soft. Mash it well with a fork and then add it in small amounts to the sauce until you like the texture.

Ingredients Needed: A single potato 

Tools Needed: Microwave and a strong fork


  • Accessible, quick, and very effective


  • Adds carbs and calories making the dish more filling

Suggestions: Potatoes have the effect of “soaking up” salt. Make sure to taste-test after adding potato!

4) Use a Roux (contains flour and gluten)

This intermediate-level technique is a powerful thickening tool. Over low heat, cook equal amounts of butter and flour. Once they simmer, add spaghetti sauce a little at a time until you obtain a velvety texture. Cook for an additional 20 minutes to get rid of any “raw flour” taste.

Ingredients Needed: Butter and flour 

Tools Needed: Whisk and a large, shallow pan


  • Confers a great Texture


  • Challenging to master
  • Time consuming

Suggestions: If you burn your roux, throw it out and start over. Nothing on the planet can disguise the taste of a burnt roux. 

Technique 2 - Thicken with Proteins

When proteins are heated, they unfold, exposing hydrophilic moieties that are eager to bind water. There are two frequent protein-based methods used to thicken spaghetti sauce.

5) Use Cheese

Let’s be honest, you were going to add cheese anyway! Instead of putting it on top of your pasta, try adding it directly to your sauce. It will thicken the sauce and give the recipe a personal spin.

Ingredients Needed: A few big handfuls of meltable cheese 


  • Adds Flavor and Texture


  • Adds a lot of Calories
  • Changes Taste and Mouthfeel of Sauce Significantly

Suggestions: Cheese burns easily--keep the stove temperature low.

6) Use Egg Yolk

When using egg yolk to thicken pasta sauce, be certain to temper the egg yolk by whisking a little hot pasta sauce into the egg first, then adding the egg mixture to the rest of the sauce. The yolk will cook too quickly if you add it to the sauce directly.

Ingredients Needed: 1-2 egg yolks 

Tools Needed: Medium bowl and whisk


  • Doesn’t alter the flavor, texture, or appearance of the sauce


  • Can ruin sauce if you don't temper egg yolk

Suggestions: Temper slowly. Add just a little hot liquid at a time, stirring constantly.

Technique 3 - Alter liquids/solids Ratio 

7) Get Rid of Some Liquid

The easiest way to eliminate liquid in a sauce is to boil that liquid away. By cooking your sauce for an additional 20-30 minutes, you should find that some liquid has evaporated, and the texture has thickened. Stir it frequently during this time.

Ingredients and Tools Needed: None


  • No extra equipment needed


  • Takes time

Suggestions: A great way to make this go faster is to use a wider pan!

8) Add Some Solids

Most people think of adding tomato puree (tomato paste) to thicken a pasta sauce. In reality, you can add nearly any vegetable that has been pureed or very finely grated. All you are doing here is increasing the surface area of the solids so that the liquid has more to cover.

Ingredients Needed: veggies of your choice 

Tools Needed: Blender or food processor


  • Nearly any veggie will work


  • Intense flavors (like beets) may overpower your seasonings

Suggestions: Grated or pureed eggplant works incredibly well!

9) Blend or Puree All / Part of the Sauce

A surefire way to thicken your sauce is to turn all or part of it into a puree. An immersion blender makes this especially easy; simply blend in increments until you find a texture you love!

Ingredients Needed: None 

Tools Needed: Blender, food processor, or immersion blender (best)


  • Extremely Easy and Effective


  • More Cleaning

How to Avoid Watery Spaghetti

Avoiding a watery sauce depends a lot on identifying what went wrong last time. One common problem is a failure to drain the tomatoes (if using tomatoes from a can).

If you are using fresh tomatoes, choose a fleshy variety that releases less water. Roma tomatoes are famously prized for this. Your heirloom tomatoes may taste excellent in a salad, but they are not likely to make the best spaghetti sauce.  

Still, other people find that the sauce only becomes watery once they add it to the spaghetti. This is the result of poorly drained, wet spaghetti weakening the sauce.

Frequently Asked Questions

Why is My Spaghetti Sauce Watery?

The most common reason for this is improperly draining your pasta. Toss the pasta in the colander to be sure it is well-drained.

How Do I Thicken Tomato Sauce Without Paste?

The article above lists several techniques that involve blending, reducing moisture, or adding starch. All of these will help you thicken your sauce without tomato paste.

How Do I Thicken Homemade Tomato Sauce?

When making pasta sauce at home, drain canned tomatoes well. If using fresh tomatoes, choose a fleshy variety such as Roma, which doesn’t release a lot of liquids when cut.

How Do I Thicken Spaghetti in the Crockpot?

Put the crockpot setting on low, but leave the lid cracked to allow moisture to escape. This will let your sauce reduce and thicken gently over time.

How Do I Thicken Spaghetti Sauce from a Jar?

If you are using pasta sauce from a jar, you probably want to use a quick and easy thickening method. The cornstarch slurry method, mashed potatoes method, or the pasta water method would all be useful (see above).


These techniques listed above work well individually or in combination. Play with several of them to find the perfect taste and texture for your signature spaghetti sauce! 

If you have any questions, don't hesitate to leave a comment below.



About the author, Caitlin Clark

Caitlin is a Ph.D student and chocolate researcher at Colorado State University. Her research in the Food Science program focuses on chocolate fermentation (that’s right, it’s a fermented food!) and small-batch post-harvest processing techniques. When she is not acting in her capacity as resident chocolate guru, she researches other fermented foods and beverages like beer, sausage, and natto. Caitlin was drawn to fermented foods while living in rural Spain for six years, where she was exposed to traditional, time-honored practices of food preservation. At home, she practices Bollywood dance for fun and is followed everywhere by two small pet rabbits.