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Smartwool Merino Seamless Bikini Review

Our testers found this pair to be an itchy, ill-fitting bikini with few redeeming qualities
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Price:  $32 List | $25.60 at Amazon
Pros:  Uncomfortable material, poor fit, expensive
Cons:  Decent drying time, naturally odor-free
Manufacturer:   Smartwool
By Lauren DeLaunay ⋅ Senior Review Editor  ⋅  Apr 3, 2019
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#9 of 9
  • Comfort - 35% 5
  • Fit - 30% 6
  • Drying Time - 25% 6
  • Packability - 10% 8

Our Verdict

Having fallen head-over-heels in love with another Smartwool product, our testing team was excitedly looking forward to testing this new, updated product. It didn't take long, unfortunately, to realize that our expectations were about to fall short with the Smartwool Merino Seamless Bikini. With a thick, itchy material and an uncomfortable, wedgie-inducing fit, we know that this model wouldn't be taking home any awards. While reasonably stretchy and breathable with an average drying time, it wasn't all bad, but the fit was the nail in the coffin for this product. For a more comfortable wool product, we highly recommend the Smartwool Merino 150 Bikini, and for our most breathable, best-fitting (and least expensive) model, the Editors' Choice Award-winning REI Co-op Active Bikini is hard to beat.

Compare to Similar Products

Our Analysis and Test Results

While the Smartwool Seamless Bikini is likely better than your average cotton undies, there are many reasons why it didn't take home an award. Its awkward fit was prone to riding up, causing significant annoyance after just a short period of wear. We also found the material to be less comfortable than the soft, silky smooth fabrics of some of its competitors.

Performance Comparison

Checking out the Seamless Bikini on our makeshift drying line.
Checking out the Seamless Bikini on our makeshift drying line.


After testing the thin, silky smooth Smartwool 150 Merino, we were a bit perplexed by the Seamless. The material is considerably thicker and itchier, which we found disappointing. We found the thick material to be less breathable than the lighter fabric of the REI Active Bikini or Patagonia Barely Hipster, also adding to this product's lower score in this metric.


Here, we considered the cut, waistband, stretch, and ability to stay in place. Nothing deters us from a difficult hike or long ski tour like a wedgie, and that's the first thing we noticed about the Seamless. The bikini cut has less coverage than some of its competitors, like the ultra-conservative Patagonia Active Hipster, but we found this to cause significantly less security on the move. The leg openings are both higher and looser than many of this product's competitors, and we found that this led to more wedgies than some of the other products we tested. While tighter leg openings may not sound appealing, a properly stretchy yet form-fitting leg opening helps keep the undies in place. The Seamless was quite disappointing in this category for this reason.

The Merino Seamless' leg openings are a bit too high for comfort.
The Merino Seamless' leg openings are a bit too high for comfort.

We found the waistband to fit well, and the undies are definitely stretchier than the Merino 150. This made them a potential contender for activities where stretch is paramount, like yoga, exercise classes, or climbing. That being said, there are products in this review that accomplish stretch alongside a secure fit, like the Patagonia Active Hipster.

Drying Time

The ability to stay dry in your base layers is incredibly important to both comfort and safety in the backcountry, as wet layers on our skin keep us colder longer. With travel undies, the ability to dry out quickly is as important to sweat as it is to travel ease. When we're on the road for weeks at a time, the ability to wash our undies in a sink or stream will keep us (and our travel partners) happy, and no one wants to sit around all day waiting for laundry to dry! To test this category, we soaked each pair in water and hung them on a line to dry side-by-side.

The Merino Seamless (right) is significantly thicker than the Merino 150 (left).
The Merino Seamless (right) is significantly thicker than the Merino 150 (left).

Despite the thicker material, we were surprised at how quickly the Seamless dried. While it wasn't as fast as the Under Armour Pure Stretch, these dried in an average amount of time, making them a decent fit for life on the road or trail.


Because these undies are used for life on the move, we considered two criteria for this category: weight and packing size. We weighed each product on our own scale to get the most accurate measurements and then judged their compactness and size next to each other.

The Seamless (left) is much thicker and bulkier than the Merino 150 (right).
The Seamless (left) is much thicker and bulkier than the Merino 150 (right).

The Seamless from Smartwool is on the heavier side of the undies we tested. At exactly 1 ounce, it's lighter than a few other models. If you're looking for a wool model that is lighter, the Smartwool Merino 150 is tied for the lightest product in this review.


The Seamless is an expensive pair of underwear. It's on the highest side of the products we tested. Without great performance, we struggle to give it much value.


One of the first things we realized about underwear was that the best products were ones that you could put on and forget about. While we enjoy an outstanding shoe or jacket, we never want to think about our undies until it's time to change. Unfortunately, the Smartwool Merino Seamless left us fidgeting and adjusting constantly. The itchy material and poor fit were deal breakers despite this product's decent drying time and stretch. For a more comfy wool option, we strongly recommend the Merino 150, also from Smartwool.

Comparing the itchy Merino Seamless (left) to the thin  silky Merino 150 (right).
Comparing the itchy Merino Seamless (left) to the thin, silky Merino 150 (right).

Lauren DeLaunay