Therm-A-Rest MondoKing 3D Review

Bottom Line

The Therm-a-Rest MondoKing 3D XXL is a standout for comfort on our best camping mattresses guide. At 4.25-inch deep, this is one of the thickest mattresses we’ve tested. Senior Gear Analyst Ian Krammer reaches for the MondoKing when he wants a reliable, recharging night of sleep at base camp. Ian spent more than 20 nights on this mattress, from the chilly depths of January in the Texas panhandle to sweltering nights in Arizona in July. Its plush design keeps it in his regular rotation.

We love the MondoKing’s plush, chamois-like surface. The inflation system is among our favorite on any camping mattress. The valve design is efficient, smooth, and durable for hundreds of refills with no issue. The oversized carrying case doubles as a giant pump sack that only takes a few minutes to fill up the mattress – a smart design that makes it harder to misplace two pieces of gear. This model has a high R-value of 7, offering top-tier insulation and warmth in colder weather. It’s as durable as they come, thanks to Therm-A-Rests’ attention to detail and high-quality construction.

However, its packed size is among the biggest of any on our camping mattresses list. This one is also a bit tedious to roll up, usually taking us two attempts until all the air is out. The pump sack design is excellent, but we find the nozzle attachment tedious to clip on. Additionally, this is one of the priciest models we’ve tested. Still, if your top priorities are comfort and warmth, the MondoKing 3D might just be the camping mattress of your dreams.

Comfort

If comfort is your top priority, the Therm-a-Rest MondoKing 3D doesn’t disappoint. While most camping mattresses on our list measure 4 inches deep, the MondoKing one-ups the competition with an extra quarter inch – and we can tell the difference. It offers exceptional cushioning with a blend of foam and air, making it one of the plushest mattresses available. The layered foam interior helps absorb uneven surfaces like roots and rocks, providing a smooth sleeping experience no matter where we set up. Gear Analyst Ian Krammer especially loves the slightly raised ribs on the surface that offers excellent support in every position from stomach to side to back.

Therm-A-Rest doesn’t skimp on the outer material, either. The supple knit exterior feels buttery-soft against the skin and won’t snag or catch on baselayers. Plus, it’s impressively quiet, making this one a great choice for even the most sensitive sleepers.

We recommend the biggest version of all our camping mattresses because the more room we have to spread out, the more comfortable we are. That’s why we tested and reviewed the XXL version of the MondoKing. However, if you’re a bit more limited on space, the Large is just as comfortable but 5 inches narrower and 3 inches shorter.

Ease of Use

Often, the simplest designs are the easiest to use, and the MondoKing is a great example. This camp mattress is self inflating, which means we simply unrolled it onto the ground and opened the intake valve. The mattress self-inflates most of the way in about 10 minutes, so you can focus on other tasks instead of wasting time inflating it by mouth or pump.

 That said, the large carrying case doubles as a pump sack to speed up the process, a handy design to get the precise firmness for you. This model comes with two high-flow valves that twist open instead of snapping – which our testers loved. The twisting design means a reduced chance of air leakage compared with mattresses with caps. When it’s time to pack up, the carrying case is plenty big enough to hold the MondoKing, and a thick nylon shoulder strap makes it easy to carry. 

We do have a couple of gripes, though. The pump sack nozzle is tricky to connect to the mattress valve. It’s a tight fit with two plastic circles. It takes some focus to snap them together, so it can slip out due to the lack of texture or threading.

Also, packing up is not as easy as setting up. The mattress is bulky, which means rolling it up requires effort. We found the MondoKing requires full body weight to deflate completely, and it usually takes two times rolling it up until it’s small enough to slip inside the bag. These are small issues, but if a speedy setup and teardown are priority, this one may not be the best match.

Warmth

Looking for a warm mattress on your camping adventures? You’ll find it in the MondoKing. An R-value of 7 can help keep you warm down to around 0°F with proper layering and a warm sleeping bag. Ian can confirm that this pad does indeed keep you warm well below freezing – the coldest he’s taken the MondoKing to is around 10°F in late December during a trip to Palo Duro State Park in Texas, where it kept him exceptionally warm. 

The extra quarter-inch of thickness is at play here, offering not only additional cushioning but more warmth by trapping heat between the layers of foam. Its durable material is designed to retain warmth efficiently, preventing heat loss to the cold ground. Whether we were camping in colder conditions or just wanted to get a cozy sleep, this mattress is one of the warmest we’ve tested. Though the high R-value is excellent for insulation, pairing it with a sleeping pad or blanket might be necessary for optimal warmth during colder nights.

Packed Size

The MondoKing is warm, but the tradeoff is that it’s also fairly bulky. If space-saving is a top priority for your camping setup, this one might not be your best bet. With a packed size of 31 by 10.3 inches, it’s one of the largest packed sizes of any on our list, so you’ll need to budget room in your trunk or storage space to accommodate this one. 

The reason it packs up so large, especially the XXL, is it’s one of the widest pads out there. The amount of foam and material doesn’t compress as well as thinner, lighter mattresses. The carrying case is a smart design with a simple cinch top opening and wide nylon strap for slinging over your shoulder. It’s not especially heavy at only 5 pounds, 8 ounces. Still, it’s a larger mattress. If you’re looking for something more compact, you might want to consider other options.

Should You Buy the Therm-a-Rest MOndoKing?

The Therm-a-Rest MondoKing 3D mattress is one of our top choices for campers who want comfort, space, and warmth when snoring under the stars. Its super thick 4.25-inch depth and decent R-value of 7 makes it one of the plushest camping mattresses out there. The XXL is an especially great choice for those who like space, with 80 x 30-inch dimensions for tons of room to stretch out. 

However, we don’t recommend this mattress if you’ve got an eye towards packed size or price. The MondoKing packs up larger than the competition, and the pump sack attachment is finicky to attach to the valve. Plus, this camping mattress is on the pricey side. However, for campers who want one of the thickest, coziest mattresses to elevate their sleep quality in the wild, the MondoKing is a great comfort pick.

What Other Camping Mattresses Should You Consider?

Our guide to the best camping mattresses lists several great alternatives to the Therm-A-Rest MondoKing:

HEST Foamy Review: The Foamy matches the MondoKing’s exceptional comfort. If you want a convenient setup, this is the one. It’s memory foam build means you can just unroll and lay down, though it’s not adjustable.

EXPED Megamat Review: The EXPED Megamat offers a similar price, comfort, and packed size as the MondoKing. However, it’s slightly heavier, a bit warmer, and not as wide or thick. 

Sea to Summit Comfort Deluxe LW Review: Sea to Summit’s Comfort Deluxe is almost as wide as the MondoKing 3D, and every bit as comfortable. It’s also slightly more affordable, packs down smaller, and has only one valve.