How to Thicken Spaghetti Sauce (With & Without Corn Starch)

thicken spaghetti sauce lg

Spaghetti sauce varies a lot in consistency. The quality of the tomatoes and using canned vs fresh all have a lot to do with it. But if your sauce is way too thin, you’ll probably wonder how to thicken spaghetti sauce.

Here’s how:

To thicken spaghetti sauce, add a cornstarch slurry (1 TBS mixed with 1/4 cup of cold water), simply simmer the sauce longer, mix in a roux, add tomato tomato paste, or use other thickening ingredients apart from cornstarch such as agar agar, potato starch, or zantham gum.

The good news is that all those aforementioned methods all work well to thicken your sauce. But if I’m being honest, adding some type of starch or thickener should be a last resort.

The reduction method works a lot better than adding a thickening agent. That’s because corn and other starches can gum up the sauce and make the texture off. So if you do gothat route, start small; you can always add more. You can’t add less.

But there’s a lot more. Read on.

Why is my spaghetti sauce runny?

Watery spaghetti sauce can be caused by using canned tomatoes with too much water in them or if, after adding the pasta, there is excess water from the pasta that was not drained off before it was mixed with the sauce.

So when using canned tomatoes (preferable except when tomatoes are at peak freshness), it’s usually a good idea to strain the excess liquid out before adding them to the pot. You can always add liquid (wine or olive oil being preferable to water). But if you have too much water, simply simmering it a lot longer is the only really good way to get the consistency right.

And if you added vegetables to the sauce, the moisture content of the vegetables could be a factor in making the sauce watery because, as you know, vegetables release liquid when you cook them down.

If you do add veggies to the sauce, it’s the salt that releases the moisture. 

So it’s always better to saute them on their own first and salt and pepper them and allow that moisture to cook off before adding it to the tomatoes.

But it could be because you did not allow your pasta sauce to simmer and reduce. It’s understandable — you could be in a hurry and were not patient enough to allow the pasta sauce to reduce enough. (Perhaps you were very hungry).

The best pasta sauces are always ones where they simmer for an hour minimum. And your Italian grandmother would argue that it should simmer all day.

How do you thicken pasta sauce quickly?

The best way to thicken pasta sauce (marinara or alfredo) quickly involves adding cornstarch. But you can also add more tomato paste to the sauce. This makes the sauce thicker without increasing the amount of liquid.

There are a couple of different ways to thicken pasta sauce quickly. Let’s check them out.

Add cornstarch slurry

Corn starch is a great thickening agent in soups and sauces. But it should not be added directly to the sauce you want to thicken, as it would clump it if you did. So, first, make a cornstarch slurry.

Simply add equal parts cornstarch and cold water and prepare your cornstarch mixture. Take a small bowl, add a tablespoon of cornstarch and add an equal amount of liquid. Stir until smooth paste forms. The ratio of cornstarch used should be the same as that of the liquid to ensure the mixture is thick. Finally, whisk the slurry into the sauce.

If your sauce is marinara sauce, you may want to use arrowroot powder instead of cornstarch. Why? Cornstarch is not very effective as a thickening ingredient when the sauce is tomato-based because tomato is acidic.

But arrow powder should not be used with milk or cream-based sauce as it tends to make the sauce slimy if it’s frozen. Don’t use cornstarch if you plan to freeze the sauce, as it can take on a spongy texture when frozen.


If your sauce has too much liquid, simmering is an easy way to have thicker sauce in a short time. You simply put the sauce in a saucepan and leave it on a stovetop at low heat or medium heat for 5 to 10 minutes.

This would ensure that the extra liquid is boiled out. Keep an eye on it so that it does not dry out but is just the desired consistency you want. It is a great way to alter the water content of the sauce while leaving the taste of the sauce unchanged.

Simmering is a simple and effective reduction process that does not require the use of additional ingredients.

Add Tomato Paste

Arguably the easiest way to have a thick sauce is to simply add tomato paste to the pasta sauce. When added to your pasta sauce, you’re increasing the number of solids in it without increasing its liquid content. The result is you’ve easily changed watery pasta sauce to one that’s got the right consistency you want.

So, you now have thick tomato sauce with an enriched tomato flavor. That would more easily stick to your pasta.

Does simmering thicken pasta sauce?

Yes. Simmering does thicken pasta sauce. It is often the preferred method for reducing the amount of liquid in a thin sauce. The low or medium heat gradually alters the liquid content of the sauce, reducing it, and a part evaporates.

If the lid of the saucepan is off. Ideally, it should be off if you want to thicken the sauce. If the lid is covered, part of the liquid content would be altered as moisture that would stick to the inner part of the lid and gradually fall back into the sauce, making it thinner!

Simmering does thicken the sauce and leaves the flavor of your sauce unchanged, but the sauce is reduced in the process, and you may no longer have as much as you would like. In that case, you may want to add a bit of cream.

One of the great things about simmering as a way to thicken your sauce is that it doesn’t take a long time (5 to 10 minutes is often okay). It’s an easy way to quickly turn your thin sauce into thick spaghetti sauce. Simmering is a simple trick to thicken your sauce with ease.

How do you make spaghetti sauce thicker without cornstarch?

You could use another thickening agent apart from cornstarch, add pureed vegetables, use flour and butter to make a roux, add egg yolks, or reduce the sauce and let it simmer for an hour or 2 longer.

Let’s find out what these entail.

Use another thickening agent

There are other thickening agents apart from cornstarch that you can use. They include arrowroot powder, tapioca, gelatin, potato starch, and others.

Add Pureed Vegetables

You can simply puree vegetables and use them to thicken your sauce.

Use Flour and Butter

You can use flour and butter in a roux or beurre manie. To make a roux, you use equal parts flour and equal parts butter. You can use all-purpose flour or bread flour.

The first step is to melt a cup of butter over medium-low heat. When it’s bubbling, add in a cup of flour. Cook the mixture until it is light brown. Then add hot liquid to the roux (two ounces of roux for every cup of liquid is the ideal ratio). Whisk it into the sauce.

To make a beurre manie, combine flour and softened butter into a thick paste, then divide the paste into small balls. Simply add these balls to your homemade sauce until you get the desired consistency.

If you like, you can add cream cheese to your pasta sauce.

Keen to know what-size-glass-baking-dish-is-best-for-1-lb-of-pasta? This is what I got into in a recent article I published. In it, I looked at how much does a 9×13 casserole dish hold and the volume of 1 pound of pasta cooked? I even revealed whether you could cook pasta dry in the oven.

Just click that link to read it on my site.

Add Egg Yolks

Separate the egg yolk from the whites, and beat the yolk with a fork until it is smooth. Add small sauce to the egg as you beat it to prevent it from scrambling. Then put the mixture in the sauce. This is the best option if you want your homemade spaghetti sauce to have a creamy texture.

Reduce The Sauce

Simply simmer the thin sauce or the watery spaghetti sauce until it is just as thick as you like. Remember to stir so that it doesn’t get burnt. And add small amounts of salt afterward, not before. Taste it before adding a lit bit more if it’s needed. If you added salt before simmering, it could end up too salty.

Simmering is probably the best method.

How do you make spaghetti sauce thicker without tomato paste?

You can add cornstarch slurry, add egg yolks, simmer the sauce, add other thickening agents, add a roux, and you can add pureed vegetables. You can also add Italian sausage or brown ground beef.

We have explored what virtually all these methods entail in the section above. They equally work for thickening watery tomato sauce or your homemade tomato sauce made from fresh tomatoes. An immersion blender would be great to puree tomatoes.

Speaking of sauces, are you wanting to know the difference between marinara and spaghetti sauce?

Check out a recent article I published. In it, I shared why it’s called marinara (you’d find it interesting) and if you can sub marinara sauce for spaghetti sauce. Ironically while most people use the terms interchangeably, there are some key differences!

Just click that link to read it on my site.

Pro Tips: Pasta has a lot of starch. Don’t forget that you can use the starchy pasta water as broth, and extra-virgin olive oil is essential the next time you’re cooking pasta sauce, and you want it to have a good texture. Your trusty slow cooker can help you prep a mean red sauce!


In the article, we looked at reasons spaghetti sauce could be runny and how to thicken pasta sauce. Then, we explored if simmering thickens the sauce and how to make spaghetti sauce thicker without cornstarch.

Lastly, we wrapped things up by considering how to make spaghetti sauce thicker without tomato paste.

Image by bluebudgie from Pixabay

Jeff Campbell

Hi! I'm Jeff Campbell. I was a leader for Whole Foods Market for over 2 decades. I worked in 9 stores in 4 states, not counting the hundred-plus stores I've assisted in other ways. I was a Global All-Star, a Gold Pen Winner, and won Top-10 Store (company-wide) 3 times in addition to Best New Store (company-wide).

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