How To Thicken Spaghetti Sauce or Pasta Sauce

Use the boiled water from the pasta

Water is typically added to a sauce that is too thin, however, pasta water is an effective thickening agent.

This is because as it boils, it will release starch. Once your pasta has cooked or nearly cooked, you can take a few teaspoons and add them to the pan containing the sauce. 

Initially, after adding the water you may notice that the sauce is a little watery, however, as you stir it you will notice that it thickens. Continue to stir it until you feel as though it has reached the desired consistency. 

A great thing about this option is that it doesn’t require the use of any additional resources. You will require a saucepan for the sauce, a pasta strainer, and a spoon. 


  • All of the tools that are required are already going to be in use.
  • The saltiness of the starch which is released into the water will add flavor to the sauce.


  • This option won’t work well with gluten-free pasta. 

Add Cornstarch to the sauce

Cornstarch is a common ingredient in many foods. It derives from corn grain and is often used as a thickening agent.

They do so through a process of gelatinization. When exposed to heat, the starch molecules swell and absorb any excess water in a liquid mixture or solution. As such, the liquid will eventually begin to thicken.

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It doesn’t have an overpowering taste and it can easily be added directly to the sauce without needing to be mixed thoroughly beforehand.

You can either stir a small amount into the sauce before allowing it to cook for a couple of minutes, or you can create a slurry by mixing a 1:1 ratio of cornstarch and water.

Once it has developed a smooth consistency you can mix it into the sauce as it simmers. Allow the sauce to cook for a further 2 minutes until it has reached a thick consistency.

Though it works fairly quickly, do not be too hasty in adding more to the sauce. When you are satisfied, you can then remove the sauce from the heat. 

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Again, you don’t require a lot of additional tools for this method apart from the cornstarch, water, a bowl, and a fork to mix it with.


  • It will not alter the appearance of the sauce or affect the taste. 
  • Starch is known to thicken as it heats.


  • There is a risk that some people may add too much before allowing it to work.

Make a roux

Roux is made from a mixture of flour and fat (typically butter) which are combined in equal parts and then cooked together. This is a slightly more advanced option that requires more effort on your behalf.

You will also need to cook it for some time until it loses its floury taste. 


The more you practice this method, the quicker you will be able to create it. To begin, you will need to set a pan over low heat. Then you will need to add butter and flour in equal quantities.

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As the roux simmers, slowly mix in your spaghetti sauce and let it cook until the texture becomes visibly thicker. The sauce is likely to take around 30 minutes to cook. It is also worth noting that due to the flour, the taste of the sauce may be altered slightly.

To make the roux, you will require butter and flour. You will also need a large pan, and a whisk to stir the mixture. 


  • The starch in the butter and flour will absorb the water in the spaghetti sauce.
  • When added it will create a sauce with a great texture.


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  • Though it is a popular option amongst experienced chefs, those with less culinary experience may find it difficult to make.
  • There are more steps involved in thickening the sauce with a roux in comparison to other methods.

Add some mashed potatoes

Although this may seem a little peculiar, mashed potato is actually a powerful thickener. This is because potatoes contain a lot of starch so it will work in a similar way to the cornstarch method.

The potatoes will alter the taste of the sauce creating a rather unique flavor, therefore it isn’t recommended for those who dislike potatoes.

If you have any leftover potatoes available, you can mash these together. Alternatively, you may peel a potato and put it in the microwave until it feels soft. Gradually, add the potato to your sauce until the texture of the sauce thickens.

Some may wish to add some milk or butter to the mashed potato before adding it to the sauce.

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Very few resources are required for this method. You will simply need a potato and a fork to mash it together. 


  • This is possibly one of the easiest options that can easily be made using leftover potatoes. 


  • Adding potatoes will increase the carbs and calories in the dish.

Change the ratio of solids and liquids


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About the Author: Thien Bao

Hello, my name is ThienBao. I am a freelance developer specializing in various types of code.