The Best Merino Wool Base Layers of 2024

A base layer is one of the most vital pieces of hiking clothing because it is in direct contact with your skin, significantly impacting your comfort level and performance. It’s our first line of defense, tasked with managing perspiration, protecting the skin from various elements such as UV rays and chafing, and maintaining the body’s natural temperature. Therefore, a base layer should be moisture-wicking, quick-drying, durable, and breathable. Hiking base layers are typically made from materials like polyester, Merino wool, or nylon. Often, blends of these materials are employed to balance out the respective shortcomings of each, ensuring we get the best possible protection and comfort on our adventures.

However, Merino wool is becoming the material of choice when it comes to base layers – exactly because it offers superb breathability and moisture wicking performance in comparison to competitive materials such as polyester and nylon. Furthermore, Merino wool is also naturally antimicrobial, super soft to the touch and provides good UV protection (read more about sun-protective clothing in this article). The natural material, however, also has downsides – it is relatively expensive, dries slightly slower than synthetic materials (see our experiment) and is often also less durable than synthetic materials. If you want to learn more about different base layer materials and their respective pros/cons, check out our Comparison of Base Layer Materials.

Here we selected and reviewed the best Merino wool base layers for hiking, mountaineering, trekking and other outdoor activities.

We deliberately listed only long-sleeved base layers as they offer great performance most of the year – on the warmest summer days  you will probably want a lighter short-sleeved base layer.

1. Our Merino Wool Base Layers Picks

1. Icebreaker Oasis Long Sleeve Crewe
2. Smartwool Classic Thermal Crewe
3. Woolly Everyday Henley
4. Ortovox 185 Rock’N’Wool
5. Minus 33 Chocorua

2. Comparison of Merino Base Layers for Hiking

Feature/Product	Icebreaker Oasis Long Sleeve Crewe	Smartwool NTS Mid 250 Crew	Woolly Everyday	Ortovox 185 Rock'N'Wool	Minus 33 Chocorua
Material	100% Merino wool	100% Merino wool	100% Merino wool	100% Merino Wool	100% Merino wool
Fabric Density	200 g/m2	250 g/m2	190 g/m2	185 g/m2	230 g/m2
Fit	Slim	Form	Regular	Athletic fit	Regular
Washing	Machine Wash	Machine Wash	Machine Wash	Machine Wash	Machine Wash
Odor-resistant	Yes (natural resistance)	Yes (natural resistance)	Yes (natural resistance)	Yes (natural resistance)	Yes (natural resistance)
UV Protection	Yes	Yes	Yes	Yes	Yes

3. The Selection

1. Icebreaker Oasis Long Sleeve Crewe

Suitable for:

• Hiking
• Mountaineering
• Trekking
• Backpacking
• Climbing
• Running
• Everyday use

The Icebreaker Oasis Long Sleeve Crewe base layer stands out as an ideal companion for a variety of outdoor activities. Crafted from 100% Merino wool fabric with a density of 200 g/m², it’s designed to offer year-round comfort, aside from the very warm summer days. What makes this base layer our personal favorite is its construction from high-quality, pure (non-blended) Merino wool, ensuring exceptional comfort alongside superior breathability, odor-resistance, and moisture-wicking capabilities. It’s tailored with a slim fit to minimize bulk when layering, yet the stretchy nature of the material guarantees ample freedom of movement. Additional thoughtful features include offset shoulder seams and a dropped tail hem; the former helps reduce chafing under a backpack, while the latter keeps the fabric from riding up and exposing your back. The Icebreaker Oasis Long Sleeve Crewe is the go-to choice for those seeking a versatile base layer capable of keeping up with diverse outdoor adventures.

Women's Version: Available - Icebreaker Women's Oasis Long Sleeve Crewe

Note: Women's version might slightly differ from the men's version.

 

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2. Smartwool Classic Thermal

Suitable for:

• Hiking
• Mountaineering
• Trekking
• Backpacking
• Climbing
• Running
• Everyday use

The Smartwool Classic Thermal base layer sets itself apart from the Icebreaker Oasis Long Sleeve Crewe with its fabric density—it’s crafted from a thicker material, making it an excellent choice for winter hiking and other cold-weather endeavors. Made of 100% Merino wool fabric with a density of 250 g/m², it offers substantial insulation, ensuring we stay warm even on the chilliest of adventures. However, it’s important to note that due to its thickness, this base layer absorbs more moisture and thus takes longer to dry compared to its thinner counterparts. The design’s snug fit further enhances insulation by preventing the escape of body-warmed air. For added comfort, the Smartwool base layer features flatlock seams and shoulder panels, eliminating seam placement in areas where backpack straps might cause irritation. Given its tight fit and heavier fabric density, the Smartwool Classic Thermal base layer is the preferred option for those of us in need of reliable warmth and protection while exploring in very cold conditions.

Women's Version: Available - Smartwool Women's Classic Thermal

Note: Women's version might slightly differ from the men's version.

 

3. Woolly Everyday Henley

Suitable for:

• Hiking
• Mountaineering
• Trekking
• Backpacking
• Climbing
• Running
• Everyday use

Seattle-based Woolly Clothing Co. specializes in creating 100% Merino wool base layers available in three distinct fabric densities—150 g/m² (Ultralight), 190 g/m² (Everyday Weight), and 250 g/m² (Mid-weight). Each category presents a variety of styles, including crew neck, v-neck, and Henley shirts, with the Everyday Weight category boasting the broadest selection of cuts. From our experience, the Woolly Everyday Henley shirt stands out for its versatility; it seamlessly integrates into any multi-layering approach for hiking while also being stylish enough for everyday wear. Its fabric density ensures adaptability across seasons, suitable for all but the warmest weather conditions. Furthermore, the Woolly Everyday Henley base layer is offered in four subdued colors, making it a tasteful addition to both outdoor gear and casual wardrobes. This balance of practicality and style makes it a favored choice among us for a range of settings and activities.

Women's Version: Available - Woolly Women's Everyday Henley 3/4 Sleeve

Note: Women's version might slightly differ from the men's version.

 

4. Ortovox 185 Rock’N’Wool

Suitable for:

• Hiking
• Mountaineering
• Trekking
• Backpacking
• Climbing
• Running
• Everyday use

For this list of the best Merino base layers, we also had to include the long-sleeved Ortovox 185 Rock’n’Wool shirt. Ortovox is a German outdoor brand with a strong focus on sustainability. This is also the case for their Merino apparel, where the wool is sourced from selected Tasmanian farms, which comply with the Ortovox Wool Promise, which is even stricter with regards to animal welfare than the Responsible Wool Standard. The brand’s 100 % Merino wool line is called the 185 Rock’n’Wool, which as the name implies, has a fabric density of 185 g/m². The unique color blocking effects on the sleeves of the base layer are bound to make you stand out in the crowd. The Ortovox 185 Rock’n’Wool base layer is thus best for those who are not afraid to make a statement, both in terms of sustainability and style.

Women's Version: Available - Ortovox Women's 185 Rock'N'Wool Base Layer

Note: Women's version might slightly differ from the men's version.

 

5. Minus 33 Chocorua

Suitable for:

• Hiking
• Mountaineering
• Trekking
• Backpacking
• Climbing
• Running
• Everyday use

The Minus 33 Chocorua base layer is made from superfine Merino wool with a fiber diameter of just 18.5 microns, prioritizes comfort and softness. This ultra-soft texture ensures the fabric feels incredibly pleasant against the skin. With a fabric density of 230 g/m², it’s perfectly suited for the cooler months of winter, fall, and spring, providing the right amount of warmth without compromising breathability. We’ve found the regular fit of the Minus 33 Chocorua to be ideal for ensuring a generous range of motion, crucial for any outdoor activity. Further enhancing its comfort are the tagless construction and flatlock seams, which eliminate the nuisances of itching and chafing. Additionally, the thoughtful inclusion of a drop tail hem prevents the base layer from riding up, safeguarding against unwanted exposure. All in all, the Minus 33 Chocorua stands out as a versatile base layer, adept at keeping you comfortable across a variety of conditions.

Women's Version: Available - Minus33 Women's Ossipee Base Layer

Note: Women's version might slightly differ from the men's version.

 

4. Buying a Merino Wool Base Layer – What is important?

Material:

Merino wool fabrics differ in density, porosity and diameter of fibers. The fiber’s diameter dictates the softness of the fabric; the smaller the diameter, the softer is the fabric. Merino wool fibers have a diameter between 17 microns (Ultrafine Merino Wool) and 24 microns (Strong Merino Wool). Base layers are usually made of fabrics with densities between 130g/m² and 250 g/m². Fabric densities under 160 g/m² are perfect for warm conditions while thicker base layers are best for hiking in autumn, winter and spring.

Merino wool can also be blended with other fibers such as nylon, polyester and polyamide to increase the lifespan (durability) of garments. However, such blends also have their shortcomings; the fabric becomes less soft to the touch and if the content of synthetic fibers is very high, the fabric also starts losing its breathability and odor resistance. For more information about Merino wool, read our article Why you should wear Merino wool clothing and this article from Smartwool.

Seams:

The seams of your base layer should not cause rubbing or chafing. To reduce any possible discomfort caused by the seams, manufacturers often use flatlock seams. Flatlock seams are particularly important when it comes to tight-fitting base layers. Read more about flatlock seams in our article What are flatlock seams.

Odor-resistance:

Merino wool is superior to any other material when it comes to odor-resistance because it contains lanolin (wool wax) which efficiently reduces odor-causing bacteria. Synthetic fabrics can be treated with antimicrobial agents to mimic this quality, but these treatments tend to get washed out fast.

Durability:

Pure Merino wool is not as durable as synthetic materials – nylon, polyester etc. However, some manufacturers blend Merino wool with nylon to increase its durability. This also allows them to make very thin and porous garments without jeopardizing their durability. Read more about the durability of Merino wool in our article How durable are Merino garments.

Fit:

The fit of a base layer has an impact on its performance; tight-fitting base layers are best for cold conditions while base layers with a regular or loose fit are best for warm conditions as they provide better ventilation.

5. Questions and Answers