Smartwool Merino Sport Ultralight Hoodie Long-Term Review

Bottom Line

  • Smartwool’s Merino Sport Ultralight Hoodie is a truly ultralight merino hoodie for hot weather.
  • I tested this Smartwool sun hoodie during a month of nonstop wear while bikepacking in Central Asia, and again while backpacking in the Pacific Northwest.
  • It’s the coolest sun hoodie I’ve tested in truly hot weather, but this comes with drawbacks like less durable fabric and incomplete sun protection. Darker colors seem to fare better.

All I wanted was a comfortable shirt that would protect me from the sun, keep me cool in scorching heat, and survive a month of non-stop biking and camping with rare showers and no laundry. Is that too much to ask?

Last summer I took a chance on Smartwool’s Merino Sport Ultralight Hoodie during a monthlong bikepacking trip in Central Asia. I needed serious sun protection for shadeless days and reasonable comfort in 90+ degree heat. I’m a big fan of other merino products from Smartwool and had high hopes for their ultralight sun hoody.

How did it do? I can certainly appreciate the challenges of designing a magic garment that meets all these needs. The Smartwool sun hoody did great in some respects and made compromises in others. I think it’s a solid option overall — in fact I recently bought a second one in a darker color and have been wearing it for backpacking — but it does have some drawbacks to be aware of.

In this detailed review I’ll explain what the Smartwool merino sun hoody excels at and what it struggles with so you can decide if it’s right for your needs.

Women’s Version Only

The Merino Sport Ultralight Hoodie seems to be exclusively a women’s shirt. The closest men’s equivalent is the Men’s Smartwool Merino Sport Hoodie, which costs $20 more and blends merino with polyester instead of Tencel. These are two different products and I’m only reviewing the Women’s Merino Sport Ultralight Hoodie here.

In some places this shirt is called the “Sport Ultralight Hoodie” and sometimes the “Active Ultralight Hoodie.” They’re the same product.

The Smartwool Active Sun Hoodie was my main shirt for over a month of bikepacking in Central Asia.
After bikepacking in the light blue Smartwool sun hoodie pictured above, I bought another one in dark blue, shown here backpacking in Desolation Wilderness.

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Smartwool Merino Sport Ultralight Hoodie (Women)

Price: $80
Weight: 5 ounces
Fabric: 53% merino wool / 47% TENCEL™ lyocell
Fabric weight: 120 gsm
Made in: Vietnam

My rating: 4 / 5 stars, performs well in many areas but with compromises

My conclusion: The minimalist Smartwool Merino Sport Ultralight Hoodie excels as a light and airy women’s merino sun hoody for hot weather. The loose fit and natural stink-resistance make it easy to wear for days or weeks on the trail, and the small hood provides sun protection without getting in the way. The breathable ultralight fabric has tradeoffs though, especially in light colors: it’s a bit see-through, not the most durable, collects dirt stains easily, and doesn’t offer full sun protection. I recommend choosing a darker color to get the most out of this sun hoodie.

Smartwool Merino Sport Hoodie Pros:

  • Light and airy fabric is cool even in very hot weather (better than any other merino sun hoodie I’ve tested)
  • Stink-resistant even on multi-week outdoor adventures
  • Minimalist design: small hood and no drawstring
  • Affordable for a merino hoody
  • Made from ethical and sustainable ZQ-certified merino wool

Smartwool Merino Sport Hoodie Cons:

  • Light colors are see-through so choose your bra carefully
  • Sunburn can occur through the fabric
  • Fabric collects dirt stains easily
  • Short sleeves and no thumb loops
  • Not the most flattering fit
  • Small hood (may be a pro for some people)
  • No drawstring (may be a pro for some people)

My Experience With The Merino Sport Ultralight Hoodie

I put the Smartwool Merino Sport Ultralight Hoodie through the wringer during a monthlong bikepacking trip in Kazakhstan and Kyrgyzstan. Aside from a spare t-shirt I kept packed away for exploring occasional towns, the sun hoody was my one and only shirt for the whole month. I wore it alone in the blazing heat of Kazakhstan’s deserts and as a baselayer in the cooler high elevations of the Tian Shan Mountains.

After returning from that trip I retired my original hoodie (learn why below) and bought another in a darker color. I’ve been testing this one while backpacking in the mountains of California and Oregon.

Testing my new darker blue Smartwool sun hoodie in the Wallowa Mountains.

Why Merino?

My favorite adventures tend to take me far from showers and laundry machines, so I’ve long been a fan of merino wool for backpacking, bikepacking, and travel. It naturally resists body odor — key for those just-one-shirt types of trips — and stays comfortable over a wide thermal range. The right weight of merino wool can add warmth on a chilly morning and yet somehow remain comfortable in the afternoon heat.

Why A Sun Hoodie?

For many years I paired merino t-shirts with sun sleeves and a neck Buff for sun protection. While this mostly prevented sunburn, the dark tan on my neck and upper arms (where sun sleeves sometimes slip down) was proof that my skin was not fully protected.

I switched to long-sleeve merino sun hoodies for my big adventures this year and I couldn’t be happier. No more fidgeting with slipping sun sleeves or hot cloth bunched around my neck. I don’t always wear the hood, but when the sun feels harsh it’s a big relief to pop it up like a magic shield. When temps drop it also adds a surprising amount of warmth.

Temperature Range

Here’s where the Smartwool Ultralight Hoodie really shines: it’s one of the few merino sun hoodies lightweight enough to be comfortable in HOT weather.

While bikepacking in Kazakhstan I experienced a few days of temps near 100 F as I pedaled across a shadeless desert. While this kind of heat is never comfortable, this hoodie felt as light and airy as could be expected.

I think this sun hoody would also be ideal, or at least tolerable, for hot and humid conditions. The heat in Kazakhstan was dry, but I’ve spent a lot of time wearing merino shirts in hot muggy climates and hate how the heavier ones stay sweat-soaked all day long.

Compared to another popular merino sun hoody I’ve been using, the Ridge Merino Solstice, the Smartwool Ultralight is much more comfortable when temperatures exceed around 75 degrees F.

Charyn Canyon topped 100 degrees F the day we visited! Fortunately this sun hoody is truly ultralight and performs well in the heat.


The Smartwool Ultralight Sport Hoodie is made from a unique blend of 53% merino wool and 47% TENCEL™ lyocell. This combination blends the quick dry time of lyocell (a semi-synthetic fabric made from cellulose fibers) with the natural thermoregulation and stink-resistance of merino wool. As mentioned above, this combination works well in hot weather and feels light and dry against the skin.

Light and breathable fabric is key to not overheating on a hot steep climb.

Sometimes this shirt is also called the “Smartwool Merino Sport 120 Hoodie” after the 120 weight designation of the merino. Many light and ultralight merino shirts are 150 weight, which I find a bit heavy for hot weather. This hoodie’s 120 weight makes it truly ultralight.

Heads up ladies: the lighter colors of this thin fabric are somewhat see-through. I wore the light blue “bleached aqua heather” color to Central Asia because I thought a light color would feel better in the heat. I sometimes felt awkward about the subtly visible outline of my sports bra (a skin-colored Patagonia Barely), especially in a region where modest clothing is the norm. The fabric was also a bit clingy.

If bra show-through is a concern for you, I’d recommend choosing a darker color. The dark blue color I’ve been testing recently has no such problem, and in hindsight I wish I had chosen it for Central Asia.

Sun Protection

Another consequence of the Merino Sport Hoodie’s ultralight fabric: it doesn’t offer the best sun protection for extreme or long-term sun exposure. In Central Asia I developed sports bra tan lines through the shirt on my back and shoulders. After getting a sunburn on one particularly exposed day I started wearing sunscreen under the shirt.

My experience in Central Asia – biking for weeks in high mountains above treeline and across shadeless desert – is probably on the extreme side. Casual users might not notice any issues, and backpackers don’t get nearly as much sun exposure on their shoulders as cyclists do. Just be aware that if you plan to wear this shirt as your sole sun protection for a long adventure, its protection is only partial.

I got sunburned through this shirt while bikepacking in Central Asia without shade for many days. It was worst when I was sweaty and the thin fabric stuck to my back.


I would describe the hood on the Smartwool Merino Sport Hoodie as “minimalist.” It works great to shade the neck, but it won’t necessarily shade your face from a variety of angles like the roomy hood on the Ridge Merino Solstice. It’s cut small and definitely won’t fit over a helmet, but it works well as a thin layer under a helmet. There’s no drawstring, but you won’t need one since the stretchy hood fits snugly anyway.

The slim hood won’t fit over a helmet but does fit nicely underneath.

I know some folks prefer a larger hood, but I like the small hood on the Smartwool sun hoody. There’s less fabric to get in the way when I’m putting on a backpack or bending down to work on my bike. There aren’t any drawstring cords flopping around on my chest. And in hot weather where this hoodie excels, the hood doesn’t add much extra warmth on my head or back.

I like that the hood is small and light enough to not flop around when I bend forward to do something, like helping to pump this Kazakh man’s motorbike tire.

Fit and Design

The Smartwool Merino Sport Hoodie runs a bit big. I’m 5’5″ and weigh 120 pounds and my chest is an A cup. I usually wear a women’s small, but in this case I returned it and bought an XS instead. The XS fit me better overall but neither size fit perfectly.

You can expect the Merino Sport Hoodie to shrink a bit once washed. I was careful to wash mine with cold water and dry it on low heat as directed, but it’s still a good inch shorter and narrower when I compare it to my new unwashed one.

I have long arms and the sleeves were a little too short on the XS, especially once I washed it. The Merino Sport Hoodie has no thumb loops. Personally I like thumb loops and the longer sleeve lengths that usually come with them, so this was a downside for me. I had to sunscreen an inch of wrist between the cuff and my cycling gloves to avoid burning.

I have a fairly long torso and thought the Merino Sport Hoodie could have been a tad longer at the hem. The overall fit was boxy and I didn’t feel especially attractive in it, but that was the least of my concerns on this trip.

On me the XS is a little boxy in the body and too short in the sleeves.

Unlike some designs that use raglan sleeves for smoothness under backpack straps, the Smartwool Sport Hoodie has seams atop the shoulder. When I wear it for backpacking the seams are not directly under my backpack straps, so they cause no problems for me.

The armholes on the Ultralight Merino Sport Hoodie are generously cut, which I really appreciate. No one enjoys the feeling of fabric bunched up in their underarm, especially in hot weather! I’m sure this also helps, along with merino’s natural stink-resistance, to keep the shirt smelling fresher during multi-day adventures.

Stink Resistance

Merino wool’s natural stink-resistance is the main reason I live in it for backpacking, bikepacking, and travel. I’ve never found a synthetic garment that stays as fresh as merino over days or weeks without a proper shower or laundry. Since this Smartwool sun hoody is only 53% merino wool (the rest being Tencel) I worried it might get a little funky during a month of remote bikepacking.

I’m happy to report that the Smartwool Ultralight Sport Hoodie was as stink-resistant as I’ve come to expect from 100% merino wool. Though showers were scarce and temps were often hot, funk levels remained manageable throughout the trip.


Ultralight merino fabrics tend to be fragile and this Smartwool sun hoody is no exception. To be fair, mine has only a single tiny hole after a month of wear. I was bikepacking though and usually not wearing a backpack. I wonder if the thin fabric can withstand rubbing from a multi-day pack during a long backpacking trip.

If you’re thinking about this sun hoodie for a long thru-hike like the PCT, you might need to ship yourself a fresh one partway through. If you’re using it closer to home I’d recommend washing it gently and not too often if you want it to last.

The light colors have a tendency to pick up dirt that doesn’t wash out. Mine became discolored with dirt and sweat stains in just a week or two. Granted I put it through a lot on that trip, but by the end it looked so grubby I was embarrassed to wear it on the plane home. By comparison, I’ve worn the Ridge Merino Solstice Hoodie for a month of similarly uncivilized bikepacking and found it much less prone to dirt stains.

If not for the dirt issue I think the longevity would be acceptable for such a lightweight shirt. Fortunately the dark blue color I’m testing now is much less prone to stains.

My hoodie is looking pretty dingy after a month of biking and camping! I’d suggest choosing a darker color if you’re planning to play in the dirt.

Price and Value

Merino clothing tends to be expensive, but at $80 the Smartwool Ultralight Hoodie is on the affordable side of the merino sun hoody range. Comparing to a few other popular merino sun hoodies: the Ridge Merino Solstice matches the $80 price tag, the Voormi River Run sells for $129, and the Ibex Indie costs a whopping $170!

Normally $80 isn’t too much to pay for a high-quality technical garment, but I would expect it to remain wearable for longer than a month. The staining and durability issues combined with the merino price premium do make this hoodie feel a bit spendy. Again, I recommend a darker color to get your money’s worth.

If budget is an issue you can find synthetic sun hoodies – like the Patagonia Capilene Daily Hoodie and REI Sahara Shade Hoodie – for lower prices. Some are better than others at matching the stink-resistance and excellent thermal range of merino, but the lightest options are quite comfortable in hot weather.

If I were buying a sun hoody for single-day use (in other words, it’s being washed regularly) I would go with synthetic for its better balance of cost and durability. But for long remote trips the stink-resistance of merino is worth the extra cost to me.

In Conclusion

After a month of heavy use my Smartwool Merino Sport Ultralight is too well-used for another big trip. I hoped it would last longer. But I liked it well enough that I bought another, this time in a darker color, for future hot-weather trips. At the relatively affordable $80 price point I’m willing to pay for a second one. So far I like the darker blue color better because it’s not see-through and doesn’t accumulate dirt stains as easily.

The women’s Merino Sport Ultralight Hoodie from Smartwool stands out for its excellent hot weather performance. Though the thin ultralight fabric comes with drawbacks, mainly limited durability and see-through light colors, it feels wonderfully light and airy. If you primarily adventure in cooler weather there are better options out there, but for temps above 80 F the feel of this hoodie can’t be beat.

For a more well-rounded merino sun hoody that does pretty darn well in hot weather and also beats the Smartwool Sport in terms of durability, thickness, and sun protection, check out the Wuru Nuyarn Lightweight Merino Hoodie.

More Outdoor Resources

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About the Author

Hi there, I’m Alissa, founder of Exploring Wild. I’ve had the pleasure of hiking the Arizona Trail, Colorado Trail, John Muir Trail, Tahoe Rim Trail, and countless shorter amazing trails throughout the US and abroad. I love solitude, big views, and a good lightweight gear setup. Learn more here.

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