How to Thicken Spaghetti Sauce – 6 Great Ways to Try

Spaghetti sauce in Italy is a glorious, thick paste that lightly sticks to the spaghetti.

Sadly, with both the sauces we buy in our supermarkets here outside of Italy and most American recipes, you end up with a sauce that is far too watery. This accounts for tomato sauces, tomato basil sauces, ones with ground beef and even my favorite – eggplant and tomato sauce.

Of course, if you buy San Marzano tinned tomatoes and crush the pulp by hand, making your homemade spaghetti sauce from scratch, you don’t need to encounter this problem at all.

However, more often than not instead of buying our speciality tomatoes from California or Campaigna, we end up using whatever is at hand in the kitchen or grabbing some canned tomatoes from the closest supermarket.

Thankfully, there are a myriad of different ways to thicken up spaghetti sauce. Below are the six most efficient methods, explained in detail and with my own recommendation of when it’s best to use which.

Why Should You Thicken Spaghetti Sauce?

You don’t need to be obsessed with all things Italian to want your spaghetti sauce thicker.

My kids, for example, wouldn’t dream of eating spaghetti that comes in a bowl of liquid, exclaiming that “it looks gross!”

Other than trying to make it acceptable to my (or your) children, a thicker spaghetti sauce will look better, taste better, and allow you to plate up the spaghetti dish you cooked up in 10 minutes as they do in professional restaurants: rolled up onto a big spoon or fork and then gently eased onto the plate, the whole dish in one, smooth sculpture.

Best Ways to Thicken Spaghetti Sauce

Which method you decide to use will depend on two things: 1) what kind of spaghetti sauce you’re making, and 2) how much time you have.

Cornstarch and breadcrumbs are the quickest methods. They work best when you’re using a jar or tin of sauce. However as well as changing the consistency they’ll also change the taste of the sauce. So if you’ve spent a good half hour making your own spaghetti sauce, these are not the best methods – unless your guests have already invaded the kitchen looking to be fed now, that is.

Thickening your spaghetti sauce by reduction is the traditional Italian method. It takes the longest, affects taste the least and works best when the sauce is almost there.

The final three methods, which work by adding a roux, egg yolk, or mashed vegetables, are all a combination of Italian cuisine with other cooking traditions. They work excellently, but should be adapted to what you’ve got in your sauce.

Reducing on the Hob

Thickening spaghetti sauce by reducing it on the hob is by far the most intuitive and traditional method. It’s what Italians use. In fact, the best bolognese is actually made using this method: for six hours, no less. It doesn’t need to take this much time, of course, but unless your sauce is almost there or if you’re using non-slow-cooked ground beef, you’re best off using one of the other five ways mentioned here. 

Simply pour the sauce into a small, high frying pan or sauce pan after having poured some olive oil into it.

Put on medium-low heat on the hob, and stir once in a while to prevent the sauce from burning to the bottom. You’ll know by the consistency when it’s done.

A good way to check is to place the back of a spoon on top of the sauce, and see how much of it sticks – this is how the sauce will stick to the spaghetti.


Thickening spaghetti sauce with cornstarch is something of a short cut, but a good one at that.

It does change the taste of the tomatoes slightly, and works best with white sauces, but if it’s a pre-bought sauce you’re using – there’s no harm done.

Keep your sauce simmering on low heat on the hob while you mix cornstarch with twice as much cold water in a bowl or cup. A whisk is good to use, as you want to make sure that you’ve got no clumps.

When you have a smooth mixture, add it slowly to the sauce while mixing. Be careful how much you put in: the cornstarch doesn’t thicken up the sauce straight away.

Five minutes on the hob should do the trick, and then you can decide if you need to add more of the cornstarch mix.


Breadcrumbs are a good alternative to cornstarch, and work in a similar way.

However, they’re a little bit easier to use and you don’t need to worry about mixing it with cold water or anything like that.

Breadcrumbs work as a thickening agent because flour does, but while flour is more likely to change the taste of your spaghetti sauce (it reacts with the acidity of the tomatoes, as does cornstarch albeit less so) breadcrumbs contain flour without changing the taste as much.

This method works best when you’re making a lot of spaghetti sauce (by a lot I mean more than one jar, if you’re using bought spaghetti sauce).

Put your sauce in a saucepan on medium heat and pour in the breadcrumbs. Stir, and keep it on a high enough heat for the sauce to simmer.

It only takes a minute or two for the breadcrumbs to thicken the sauce, so if you’re in a rush – this is the way to go.

Using a Roux

A roux is the basis of one of the cornerstone sauces of French cuisine, bechamel. It’s also a great way to thicken Alfredo sauce.

This is a very wholesome method, and it’s a way to use flour as a thickener without having it react with the acidity of the tomatoes. It doesn’t change the taste of your sauce, so the only downside here is if you’re on a diet, since you’ll need to use quite a bit of butter. 

Leave your spaghetti sauce to simmer in a sauce pan on the side.

In another saucepan on medium-low heat, melt butter and combine with flour. You’re going to want to put the flour in before the butter is fully melted, to avoid it burning and sticking to the pan.

A good proportion for tomato-based sauces is to use as much flour as butter.

With a wooden spoon, quickly combine the two until you’ve got a smooth mixture. Keep on low heat until it smells of biscuits, and then stir or whisk into your spaghetti sauce.

Egg Yolk

Another French method for thickening spaghetti sauce is by using egg yolk.

In many French takes on spaghetti, it’s served raw on top of the pasta and combined on the plate, but here we’re going to have a look at how to use it before serving.

Egg yolk works well as a thickener because it’s rich in protein, which binds the proteins in the sauce together. This works great if you’re using meat or dairy products in your sauce, as the protein reaction is stronger while the egg yolk taste is a great addition to these.

A benefit of this method is that you can add the yolk when everything’s already done, so it requires no cooking time at all. It’s also a great way to add some more protein to your diet!

To thicken spaghetti sauce with egg yolk, first combine the sauce and the spaghetti in a big sauce pan.

Create a “well” in the middle of the pasta – it doesn’t need to go all the way to the bottom of the pan, but should go at least a third of the way.

Separate an egg and drop the egg yolk in the “well” you’ve made for it. As the pasta is hot, the yolk will start cooking immediately, so you’re going to want to be quick here and mix the pasta, the sauce and the yolk together.

If it’s still not thick enough, repeat the process again by adding another yolk. For a serving of three people, I would suggest not using more than two yolks unless you want the egg flavor to be a part of your dish.

How to Thicken Spaghetti Sauce with Mashed Vegetables

Apart from the reduction method, adding tomato paste is the most common, traditional and easy way to thicken up spaghetti sauce. You can add as much as a tablespoon per serving.

With tomato sauce, as with any other vegetable added, you want to cook the sauce on medium heat and stir it thoroughly when adding in the paste.

However, tomato paste is not the only thing you can use. You can also use mashed tomatoes, butternut squash, potatoes, sweet potatoes, eggplant or even cauliflower.

Butternut squash, potatoes, sweet potatoes and cauliflower work great and add some sweetness to the sauce. They are all rich in starch, working therefore similarly to cornflower and binding the spaghetti sauce together. Cooked and then mashed, add a tablespoon or two to your sauce, let it simmer for a while, and then it’s ready to serve. Make sure you’ve got enough salt in the mash as the starch means they need to be quite salty. 

For mashed tomatoes, take off the skin by leaving them in boiling water for a minute, placing them under cold running water and then peeling with a knife.

Cut the tomatoes open, throw away the liquid and seeds at the core, and use only the harder, outer layer. This you can mash up with a blender or by hand on a chopping board with a knife. For a spaghetti from the supermarket, this is a great way to make it taste fresher. Make sure to cook the tomatoes and the sauce for at least ten minutes on medium heat.

Mashed Eggplant

My personal favorite vegateable to use is to add mashed eggplant.

It’s a delicious addition to basil and tomato sauce, and a great way to spice up a store-bought jar of Barilla sauce.

For this, you’re going to want to pre-cook the eggplant by either putting it whole in the oven, covering it with aluminium, cooling it down and then taking the skin off – or burning it on an open flame on a gas hob.

By burning the skin on all sides, you’re also cooking the eggplant inside, so that when it’s cooled down and ready to be de-skinned by hand, you have “mush” to make finer with a knife on your chopping board and then pour into the sauce itself.

Stir well and keep simmering the thickened sauce for another five-six minutes, add some more salt and you’ve got a delicious, creamy spaghetti sauce.