Monterey 5ist Car Seat Review

The best car seat is the one that fits your child, vehicle, budget, and lifestyle and has the features important to you. The safest car seat is the one you can install correctly and use properly on every ride! Let us know in the comment section what questions you have about this review of the Diono Monterey 5iST booster seat. And if you want to compare car seats and let us help you find your recommended car seats, our Car Seat Buying Kits are your best bet!

Diono Monterey 5iST (US/Canada)

In this review, we’ll take a close look at why the Diono Monterey 5iST booster may be a good option for your booster-aged child. It’s a nice option for parents who travel often since it folds up. Additionally, if you have non-removable headrests in your vehicle, this is one of the high-back booster options that will work. This is a great high-back booster option for higher-percentile kids as well.


A high back-only booster seat


From 5+, but the child must be mature enough to sit properly at all times


From 5 years until outgrown (10-11 years of age)

What you need to know before you go.*

Monterey 5ist Car Seat Review

Forward-Facing Stats

  • height limit: 38-63″
  • weight limit: 40-120 pounds
  • head height rules: ears must be contained within the headrest

Other Seat Stats

  • width of seat: 23”
  • weight of seat: 18.7 pounds
  • crash replacement policy: replace after a moderate or severe crash
  • expiration limits: 8 years

*Head to the Car Seat Buying Kits for a complete database of all car seat stats for our recommended car seats.

✅ Seat is Good for You If:

✅ You frequently use Lyft/Uber/Taxis.
Monterey 5ist Car Seat Review

The Diono Monterey 5iST works well in most vehicles. It folds up to make it easier to carry around as well. But the backpack-style straps also allow you to wear it instead.

✅ You travel often.

This seat folds up to the size of a carry-on so it can be stowed in the overhead compartment of many planes. This makes it a good option for parents who want to take a high back booster on their family trips.

✅ Your vehicle has non-removable headrests.

This booster is one of the few options that works well with non-removable headrests because it does not have to be flush with the vehicle seat. Other options that work with these kinds of headrests are Nuna Aace, Clek Oobr, any of Peg Perego’s boosters, any of the other Diono boosters, and Evenflo’s boosters.

✅You have a tall child.
Monterey 5ist Car Seat Review

This high back booster has 63″ limits, which is currently the maximum standing height limit available for boosters. It also has a very tall belt guide that can accommodate a child until their torso height is around 21″.

🚩 Use Caution If:

🚩You want a booster that converts to backless as well.

This is a high back booster only. But it has a very tall headrest, so it will accommodate most children until they can fit properly in the seat belt.

🚩You want a lightweight option to move between different vehicles.

This booster weighs almost 19 pounds. With some boosters as light as 5 pounds, this is quite a heavy one. But it’s still not as heavy as many convertible car seats are, so this one may be ok for you!

🚩 You need to fit 3 across in a vehicle.

I can’t imagine the Diono Monterey 5iST fitting 3 across in any vehicle, since it’s one of the widest seats on the market. Check out our blog post on fitting 3 across here to find some better options.

🚩 You are planning to use it in a vehicle seat without a headrest.

Diono requires that the vehicle’s head support is at least as high as the top of the child’s ears, so if your vehicle does not have a headrest in the seating position you were considering using, you will either need to choose a different seating position or a different high back booster.

⭐️ Stand Out Features:

⭐ It folds!
Monterey 5ist Car Seat Review

We love that this booster can fold. This makes it easy for parents who want to have an extra booster in their trunk for carpooling or for parents who travel often. It makes storing it in your house easier as well!

⭐ It has rigid lower anchors
Monterey 5ist Car Seat Review

Lower anchors on the booster are optional. But if you don’t use the lower anchors, then you need to buckle the seat belt whenever the child is not riding in the vehicle with you. The lower anchors on this seat are rigid, which makes them easy to attach in many vehicles.

⭐ It has backpack-style straps to carry it around easily

After folding up the seat, you can utilize the attached straps to carry it around like a backpack. This can be a good option for parents who don’t own a vehicle but prefer to have a high back booster.

▶️ YouTube Videos

▶️ Best Car Seat for Travel

▶️ Why Your Kid Will be in a Car Seat for 10+ Years

✈️ Airplane Use

Like all boosters, the Diono Monterey 5iST does NOT have aircraft approval. But because it folds up, this is still a great option for airplane travel. When folded, it’s small enough to take as carry-on luggage for most airlines. For help with all things airplane travel and car seats, check out our Wheels Up Course and private Facebook group.

SITS Bottom Line

In conclusion, the Diono Monterey 5iST high-back booster seat is a standout choice for parents who demand flexibility, ease of use, and top-notch safety for their children. Its foldable design, rigid lower anchors, and backpack-style carrying straps cater to the needs of busy families on the move. Whether you rely on Lyft, Uber, or taxis, frequently embark on family adventures, or have a vehicle with non-removable headrests, this booster seat has you covered. While it may not convert to a backless booster, its tall headrest and impressive height limits ensure your child’s comfort and safety. Remember, when it comes to travel, the Diono Monterey 5iST is a reliable companion, with its compact fold making it suitable for overhead compartments on planes. So, whether you’re hitting the road or taking to the skies, this booster seat is your trusted partner for safer and more convenient journeys with your child.

Other Versions of This Seat

Diono Monterey 5iST FixSafe* – Canada

*A SITS recommended seat. Recommended seats are in our Buying Kits because they have ranked high on our vehicle, child, ease of use, and features scales.

Compare Car Seats

Looking to compare car seats and narrow down the best car seat for your family? The Forward-Facing and Booster Buying Kit walks you through our 7Cs of selection, then on to an interactive quiz. And finally, a recommended car seat list is generated just for you! If you are overwhelmed and sick of spending hours researching and reading car seat reviews like this one, the Buying Kit will guide you to Safe in the Seat’s recommended car seats for you in under 30 minutes!

recommended car seat sales

We check every day for our recommended car seats on sale, and we have all the deals here for you. Shopping in Canada? Find today’s seat sales in Canada here.

What About Seats We Don’t Recommend?

Just like anyone, we have preferences! This goes for car seats, too. If we don’t recommend a car seat, it’s not because it’s unsafe for your little one. All car seats are safe if they’re installed and used properly, are not expired or damaged, and when they’re made and sold by a reputable manufacturer and/or retailer. Click here for our full list of car seats that we do not recommend.

A note about crash-tests

How does the Diono Monterey 5iST perform in crash tests? 

Well, that’s a great question. We know that it passes the strict federally required testing that applies to all car seats sold in the United States. But we don’t know exactly how it performs. That data isn’t released by any official sources in the US — not by car seat manufacturers, not by government agencies like NHTSA, not anywhere! 

There are a few third-party websites that claim to offer objective crash test data for a variety of car seats. But we at Safe in the Seat don’t pay attention to that data for a few big reasons. First of all, third-party crash tests don’t actually give us meaningful data! Car seat manufacturers crash-test their products hundreds, even upwards of a thousand times. They crash test the finished product in every single installation configuration using every applicable-sized crash test dummy, not to mention a whole lot of testing at each stage of the development process too. So one or two crash tests completed by another organization just can’t give the same level of information! One or two crash tests aren’t going to represent the overall average performance of any car seat across its lifespan.

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