Simplicity That Delivers: Smartwool Classic Thermal Merino Women’s Base Layers Review

In a world full of flashy features, hybrid fabrics, and techy gear names, the Smartwool Classic Thermal Merino Crew Top and Bottom take a refreshingly straightforward approach. Formerly known as the Merino 250 base layers for women, these all-wool essentials don’t bother with bells and whistles — and they don’t need to.

What they do offer is warmth, comfort, and reliability across everything from powder days in Aspen to long-haul travel in the Italian Dolomites. They fit well, don’t stink, and keep you warm without ever getting in the way.

In short: The Smartwool Classic Thermal Merino Crew Top ($115) and Bottoms ($115) are high-quality, high-performing women’s base layers that excel in cold-weather comfort without overcomplicating things. The fit is trim but forgiving, with enough length in the top to stay tucked and a wide, flattering waistband on the bottoms that doesn’t dig or slide. They’re warm enough for 20-degree ski days, breathable during activity, and impressively odor-resistant: I wore them 5 days straight in the Dolomites without a whiff of regret.

See how these thermal layers compare to our other favorites in the Best Base Layers for Women buyer’s guide.

Testing Conditions: Smartwool Classic Thermal Women’s Base Layers Review

I’ve tested dozens of women’s base layers over the years, from ultralight blends to fleece-lined synthetics and thermo-regulated options. While many try to stand out with high-tech gimmicks, few deliver on the everyday reliability of Smartwool’s Classic Thermal Merino set.

I wore the top and bottom constantly this winter — from skiing deep powder in Aspen to layering up for long travel days in northern Italy. The latter included a 5-day continuous stint in the Dolomites without regret. Whether I was chasing warmth, mobility, or all-day comfort, these layers delivered without fail.

Trim, Long, and Flattering

Let’s talk about fit because base layers for women can go either way. If they’re too loose, you feel like you’re wearing a baggy diaper beneath your snowpants. But if they’re too tight, you feel like you’ve been rolled into a sausage casing that may pop at any moment. Luckily, Smartwool nailed it with this set.

The Classic Thermal Merino Crew is cut close to the body so it has a flattering, trim aesthetic, but it’s not clingy — and it doesn’t latch onto skin rolls in weird ways. And, it’s long enough to stay securely tucked into snow pants all day, which is a huge win. No pulling, no bunching, and no surprise lower-back breeze when you reach for a ski boot buckle.

The bottoms feature a wide, flattering waistband that doesn’t dig into your stomach or roll when you’re on the move. It’s high enough to feel secure but not restrictive, which makes it comfortable under ski bibs and equally easy to lounge in at après. Functionally, they fit the way you want a base layer to fit: like a second skin you don’t need to think about.

Tradeoff: I tested a set in the Winter Sky Heather color, and it’s beautiful … but transparent. It’s fine on the shirt, but I quickly realized I couldn’t run into the grocery store without flashing my friends. I’d recommend a darker shade.

Reliable Warmth in Cold Temps

I wore this set on multiple ski days in the low 20s in Aspen, Colo., and felt toasty every time — even during windy lift rides, shaded tree runs, and cold transitions in the parking lot. The fabric does a great job of regulating body heat, keeping sweat from turning into a post-run chill, and drying quickly once you’re inside, peeling off layers while devouring a slice of pizza or sipping a mid-morning coffee.

Technically, this is a 250-weight base layer, which Smartwool rates at 218 grams per square meter (gsm), putting it firmly in the midweight category. That makes it heavier and warmer than lightweight wool, but not as thick or insulating as heavyweight layers. That said, it feels a bit toastier than your typical midweight, likely due to the dense knit and full merino construction.

It became my go-to on a wide range of ski days because it struck a sweet spot between warmth and mobility. Whether I was carving groomers, hiking with our puppy, or chasing my daughter through an icy trailhead parking lot, the fabric moved with me without overheating.

That said, when temps dipped into the low teens or single digits, I needed to add another layer or opt for something heavier. It’s not the warmest base layer in my closet, but for the majority of winter adventures, this one was the most versatile.

Odor Resistance That Works

Smartwool’s merino has long been praised for its natural odor resistance, and this set continues to uphold that reputation. Thanks to the 100% merino wool construction, these layers resist stink far better than synthetics.

That’s because merino fibers naturally trap odor molecules and lock them in until the garment is washed — a built-in defense system that keeps you from smelling like a locker room, even after days of wear. Plus, wool is breathable and moisture-wicking, which helps reduce the sweaty environment bacteria need to thrive.

I put this to the test on a ski trip to Italy, where I wore the same top and bottom for five consecutive days at Dolomiti Superski. The conditions ranged from snowy and cold to hot spring-skiing sunshine, meaning I was sweating, layering, and stripping down constantly, especially when I tried — and failed — to race my daughter through the terrain park! And yet, no smell.

After each day, I’d peel them off, let them air out, and toss them back on in the morning like the dirtbag I am. Even after ski-to-après transitions at a fancy hotel (where I wore the crew top like a regular long-sleeve shirt at the bar), I never felt like I was that person. In fact, I even wore the top on the flight home — no shame, no stink, and no need to change in an airport bathroom.

Room for Improvement

While I love almost everything about these layers, the bottoms did stretch out slightly after a few days of use. The butt was a bit saggier by day four or five, and I noticed it more when I wore them off the mountain. I think sitting is what really stretches them out. It wasn’t enough to cause any technical issues, but it was noticeable and made the fit feel less polished by the end of the trip.

As I mentioned, the light color is too transparent — especially on the bottoms — for conservative errand-running sans snow pants.

The only other sticking point is the price. At full MSRP, the top and bottom run at $115 each. That’s a hefty investment for women’s base layers, but it also reflects the high-quality merino and dependable performance you’re getting. If you live in wool base layers all winter (like I do), they’re worth it.

Final Thoughts

There’s nothing flashy about the Smartwool Classic Thermal Merino Base Layers — and that’s exactly why I love them.

They do what base layers should: keep you warm, wick sweat, resist odor, and disappear under your outerwear so you don’t even think about them. No frills, just function. And when you’re halfway up a mountain or 5 days into a ski trip, that’s exactly what I want.