Smartwool Merino Sport 150 Boxer Brief running underwear review: comfort like this comes at a price

Excellent, ready-for-action undies, Smartwool Merino Sport 150 Boxer Briefs are made from the nature’s magic material – merino wool

Smartwool Merino Sport 150 Boxer Brief
(Image: © Smartwool)

Advnture Verdict

Box clever in these smart woollen undies, absolutely ideal for use while running, riding and hiking in a range of climates and conditions.


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    Super comfortable

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    Natural fiber

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    Moisture wicking

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    Odor control

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    Plastic-free, 100 per cent recyclable packaging


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    No fly

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Smartwool Merino Sport 150 Boxer Brief: first impressions

First up, let me wax lyrical about the main fabric in the Smartwool Merino Sport 150 Boxer Brief. I’m a massive merino wool fan, and I will always reach for a base layer made from this magic material for my upper half. I must admit, though, I’ve never worn woollen undies before. So, in the spirit of advnture… here goes. 

Merino wool is a superb material. Its next-to-skin feel is lovely, it keeps you cool when the weather is oppressively warm, and warm when conditions are cooler; it wicks moisture away from the skin, so you’re less likely to chafe or develop hotspots when sweating; and it can even deal with odor management. 

All of the above makes it perfect for use in underwear, so why aren’t we all always wearing merino keks? While, the price is one reason – 35 bucks for a pair of underpants is butt-clenchingly steep for most people, I think it’s fair to say – so let’s hope they live up to my high expectations and how they measure up against their rivals in our best running underwear buying guide.


• RRP: $35 (US) / £35 (UK) / €39.95 (EU)
• Gender specificity: Male
• Style: Boxer brief
• Materials: Merino Wool (56%), polyester (44%)
• Colors: Black / Moss Green Heather / Gray Heather / Argyle Purple Heather / Picante
• Sizes: S / M / L / XL / XXL

Smartwool Merino Sport 150 Boxer Brief: on the trails

Unsurprisingly, given all of the above, I found these boxers wonderful to wear while trail running, hiking and biking. They are extremely comfortable, but you do know they’re there, because they are reassuring supportive too. 

They manage sweat build up brilliantly, and the natural anti-bacterial properties in the merino material make the Smartwool Sport 150s perfect for use during longer adventures, such as ultras, overnight hikes, fastpacking and bikepacking escapades. 

Merino is also a natural fiber (wool), so it’s biodegradable and considerably better for the environment. The only downside to merino we’ve ever really come across is that it does tend to wear through relatively quickly, but the combination of polyester in these pants means they will last the distance. 

Beyond the materials, the design is excellent, with a double front panel, and a wide waistband that’s effective in keeping the pants in place, and makes them comfortable to wear (even this band is covered in merino, to maintain the sumptuous next-to-skin feel throughout the whole garment). 

The seams are flatlocked too, which also adds to the comfort. As mentioned, all this comes at a pretty stiff price, however. And there’s also no fly, if that kind of thing bothers you (it didn’t worry me to be honest – answering a call of nature as a bloke is hardly rocket science).

Pat Kinsella

Author of Caving, Canyoning, Coasteering…, a recently released book about all kinds of outdoor adventures around Britain, Pat has spent 20 years pursuing stories involving boots, bikes, boats, beers and bruises. En route he’s canoed Canada’s Yukon River, climbed Mont Blanc and Kilimanjaro, skied and mountain biked through the Norwegian Alps, run an ultra across the roof of Mauritius, and set short-lived records for trail-running Australia’s highest peaks and New Zealand’s Great Walks. He’s authored walking guides to Devon and Dorset, and once wrote a whole book about Toilets for Lonely Planet. Follow Pat’s escapades on Strava here and Instagram here.