Best Merino Wool Long Underwear

Updated November 2022
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Best of the Best
Smartwool Men's Merino 250 Baselayer Bottom
Men's Merino 250 Baselayer Bottom
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Trusted Brand
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Our fitness expert recommends the comfort and superior construction of Smartwool. Perfect as a base layer for winter tent camping, backpacking, for very cold temperatures.


Interlocking natural fibers keep the cold out, despite being lightweight and breathable. Designed to wick away sweat and prevent chafing. Slim-fitting for wear under other clothing. Traditional fly for convenience.


Since they're designed to be thin, a few found tears after extremely vigorous activity.

Best Bang for the Buck Merino Wool Base Layer
Merino Wool Base Layer
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Versatile & Affordable
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These base layer pants are praised for their versatility in situations that fluctuate between cold and warm temperatures.


Midweight, 18.5-micron. Flexible 250g material. Naturally resists odor and wicks moisture away from the skin. Comes with a pair of matching socks. Safe for machine-washing and drying, although hand-washing is recommended for longevity.


A few complaints about holes, as well as questions about their authenticity.

Hocosa of Switzerland Women's Long Underwear
Hocosa of Switzerland
Women's Long Underwear
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Unique Design
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This lightweight blend of organic materials can stand up to skiing or hiking as well as lounging.


Smooth, with a blend of 30% silk. Thin to the touch, but warms like thicker, bulkier products. Slim-fitting with generous stretch. Designed to wick away moisture. The natural lanolin allows these pants to go weeks without washing, even with daily wear.


The waistband has a tendency to roll. Some complained that the fabric felt itchy.

MERIWOOL Men's Base Layer Merino Wool Thermal Pants
Men's Base Layer Merino Wool Thermal Pants
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Most Comprehensive
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This quick-drying pair earns high marks from our fitness expert for its moisture-wicking and odor resistance over lengthy hikes.


Made with a fine interlock knit. At 250g, it's breathable but still prevents cold drafts. Designed with convenient loop for easy drying while out on the trail. Owners attest to its comfort and barely-there feel as a base layer.


Must be machine-washed on cold. Some found them snug at the waist. Consider sizing up if choosing between sizes.

Icebreaker Women's Everyday Leggings
Women's Everyday Leggings
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Simple Yet Solid
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These slim-fitting leggings add an extra layer of warmth during daily errands or more adventurous outings.


Designed with a flat, brushed waistband that won't roll. Thinner 175g weight good for staying warm around town as well as backpacking and camping. Can be machine-washed and dried, but many users recommend hand-washing to increase longevity.


Intentionally designed to be thin, these cannot be worn alone like athletic leggings. Pricey.


We recommend these products based on an intensive research process that's designed to cut through the noise and find the top products in this space. Guided by experts, we spend hours looking into the factors that matter, to bring you these selections.

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Buying guide for Best merino wool long underwear

If you’re going to spend time in colder conditions, you might already be thinking about layering. It can get pretty bulky, and if you’re wearing several layers, it can be downright uncomfortable, not to mention laborious to disrobe. That’s why it’s time to invest in merino wool long underwear, a thin base layer that can keep you warm and eliminate the need for multiple layers.

Merino wool long underwear can be made of 100% wool or a blend. Both types provide superior warmth and comfort compared to traditional fleece or thick outerwear. Since long underwear is designed to be a base layer, it’s easy to wear under a pair of jeans or pants all day. As a matter of fact, long underwear is so comfortable, it’s used by outdoor enthusiasts, people who work outside, and the average person spending time in low temperatures. Unlike other garments and outerwear, it can last for years if it’s well cared for.

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If you’re concerned about exposing your long underwear when you bend over, look for options that are the same color as your jeans or pants.

Key considerations

Benefits of merino wool

Merino wool comes from sheep, and sheep produce large amounts of lanolin that coats the wool to protect it from the elements. As a result, merino wool naturally repels moisture, provides UV protection, and is one of the least combustible textiles. It also has high tensile strength, making it incredibly durable. Merino wool is naturally odor resistant, so it’s a favorite among outdoor enthusiasts and professionals who work in all climates.

Merino wool is a natural insulator. You might be surprised to know that despite its seemingly tight weave, it has microscopic holes to be breathable. That’s why merino wool is considered an all-season, all-climate textile. It’s capable of keeping you warm in cold temperatures and comfortable in warmer environments.

Expert tip
For a multi-day backpacking trip, most merino wool long underwear can be worn for several days without washing due to its superior wicking properties.
BestReviews Fitness Expert


When you shop for merino wool long underwear, you’ll see a number associated with the fabric. Grams per square meter (gsm) is the weight of the wool on a scale of 0 to over 250. Even if the weight isn’t apparent in the description, manufacturers will usually offer the grams per square meter to simplify things.

  • Very lightweight wool: Less than 150 gsm

  • Lightweight wool: 160 to 190 gsm

  • Mid-weight wool: 195 to 250 gsm

  • Heavyweight wool: 250 gsm and higher


You can find merino wool long underwear in men’s, women’s, and unisex sizing. For the most part, it’s easy to find big and tall sizes for men’s long underwear, which isn’t always true for other clothing. Some brands provide the inseam length, which is important if you’re tall. You want the underwear to be long enough to keep you warm, including your ankles. Styles that utilize inseam sizing tend to be a little more expensive, but at least you’re guaranteed a better fit.

Women’s sizes run the gamut as well, but it’s harder to find plus-size long underwear. As far as unisex sizes, these don’t always provide the greatest fit, though sometimes this long underwear is less expensive than gender-specific sizes.

"Tuck your base layer shirt into your long underwear to prevent cold drafts from coming up inside your clothing."

Merino wool long underwear features


Most merino wool long underwear is black or ivory. Certain brands offer a wider color assortment, especially those that have caught on to the trend of wearing long underwear as outerwear. In addition to plenty of solids, you’ll also find stripes and camo-themed options.


Merino wool long underwear is made from either 100% merino wool or a blend containing wool.

  • 100% merino wool: In terms of quality, all-wool long underwear is superior because you get all the benefits of wool without being derailed by inferior materials. As a result, 100% wool long underwear is far more expensive than other types.

  • Blends: Merino wool long underwear made of a blend usually includes around 30% merino wool combined with cotton, Lycra, spandex, polyester, acrylic, and/or silk. Each material offers something different, though they also take away from the qualities of pure merino wool. Cotton, for example, is a soft, breathable material, but it holds onto moisture. Some consumers feel long underwear made of blends doesn’t have the same tensile strength as 100% wool and is more susceptible to wear and holes.
expert tip
Look for long underwear that has a loop inside them which allows you to hang dry them at campsites.
BestReviews Fitness  Expert

Merino wool long underwear prices

Merino wool long underwear costs between $15 and $100, and more often than not, people get two at a time to alternate between washings.


The least expensive merino wool long underwear includes blends with about 35% merino wool. These cost between $15 and $35.


This long underwear may be 100% merino wool and costs between $35 and $55. Long underwear in this price bracket is also well constructed, true to size, and generally more comfortable.


If you’re willing to spend closer to $100, you can find top-quality 100% merino wool long underwear. These garments far outlast their inexpensive counterparts, making them well worth the higher price.


  • Give merino wool long underwear to an outdoor enthusiast. Merino wool long underwear is a useful, thoughtful gift for the avid hiker or camper in your family.

  • Wash long underwear separately. Even though merino wool long underwear is machine washable, it’s a good idea to wash it separately so you don’t accidentally include it in a load with fabric softener.

  • Look for long underwear with flat seams. If you have sensitive skin, opt for a style that features flat seams to reduce chafing and keep skin irritation to a minimum.

  • Pack light. If you’re going on a trip to a cold destination, you can pack light by relying on merino wool long underwear to keep you warm. You won’t need as many bulky items, so packing a pair or two can save a lot of space in your luggage.
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If you’re over 6’2”, you might need to opt for big or tall sizes to accommodate your inseam. Refer to the manufacturer’s size guide to make sure you get the right fit for your height.


Q. Will I be warm enough with merino wool long underwear, or do I also need matching tops and socks?

A. It really depends on your preference and where you’ll be. Having a 100% merino wool base layer neck to toe will undoubtedly keep you warm. If you feel like that’s too much, you can stick with your regular tops, socks, and outerwear. With that said, if you’re spending a lot of time outside and don’t have sufficiently lined footwear, it’s not a bad idea to invest in merino wool socks as well.

Expert tip
I highly recommend purchasing long underwear with flat seams since this will prevent chafing and skin irritation.
BestReviews Fitness Expert

Q. How do I fix a hole in merino wool?

A. If you intend to sew it up yourself and you’ve never done it before, you’ll need the right needles, thread, and probably an online tutorial. It’s not an intimidating project, but it requires time and patience so the wool doesn’t pucker at the repair site. You could take it to a tailor if the cost to repair it is reasonable and less than the price of a replacement. Another option is to contact the manufacturer and see if the garment is covered under any protection or satisfaction guarantee.

Q. What’s the best way to wash merino wool long underwear?

A. Each manufacturer details recommended care instructions on the label. As a general rule, it’s recommended that you wash the long underwear in warm or cool water with regular laundry detergent. Stay away from products that include bleach or other harsh chemicals, and refrain from using fabric softener. While some merino wool garments indicate that you can put them in the dryer, you can extend the life of the garment by simply air-drying it.

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