Last Updated on 27/08/2023
In this guide to the Best Merino Wool Base Layers, we share the warmest, lightest, most breathable, and most comfortable base layer tops made from merino wool. You will learn why merino wool works so well for thermal underwear and how you should think about layering them.
Wearing the Best Merino Wool Base Layers is one of the easiest ways to retain body heat without overheating or restricting movement. If you value your warmth, comfort, and pack weight, then base layers made from Merino wool are highly recommended and worth hunting down. Obtained from the fibers of sheep that come from some of the most extreme regions on earth, Merino wool holds properties that synthetic fibers can’t compete with.
For full-body warmth, you can add a pair of merino wool base layer pants and some merino underwear too if you like. We do also have a guide to hooded base layer tops, which are mostly made from merino wool too. There are so many choices, but in this article, we are specifically looking at long-leave base layer tops made from merino wool or a merino blend.
Why not go full merino wool? In the ideal world, all clothing would be made from merino wool, but one reason why this might not be practical is that merino wool is expensive. If you are new to merino wool or simply want to understand why it is so special, then check out these 17 benefits of merino wool.
Top 10 Best Merino Wool Base Layer Tops
Ice Breaker Apex Crew Base Layer Top
- Material: 240 Midweight, 100% Merino Wool
- Weight: Medium = 310 g / 10.93 oz
The Icebreaker Apex Crew is a super durable midweight base layer that works great as both your first and only level of protection. What this means is that not only does it keep you warm underneath your other clothes in cold weather, but it also makes the perfect hiking shirt in hot weather.
With a handy secure zip pocket on the left-hand sleeve, it is perfect for keeping cash, cards, keys, etc… The thumb holes on the sleeves allow you to cover your knuckles as well as serve to keep the cuffs tucked into your gloves in winter.
Off-shoulder seams prevent back rubbing with a heavy pack, and flatlock seams prevent chafing with repetitive motion. The drop tail hem hangs slightly lower at the back and keeps your shirt tucked in at the back when you are stretching or bending down.
VERDICT: Super breathable and comfortable, the Icebreaker Apex Crew is a Gear Assistant favorite that has rightly earned its place at the top of this list of the best merino base layers.
Minus33 Merino Wool Chocorua Midweight Crew
- Material: 230 Midweight, 100% Merino Wool
- Weight: Large = 315 g / 11.2 oz
The Minus33 Chocorua Midweight Crew is one of the best Merino Wool Base Layers on this list, named after a mountain in New Hampshire and is Minus33’s most popular men’s top. The interlocking knit construction is surprisingly hard-wearing while feeling super light.
Like the Icebreaker Apex, the Minus33 Chocorua works as both a base layer and a standalone outer layer. The 100 % merino wool is odor resistant as well as machine washable and dryable for backpackers and hikers who might not get too many chances to do laundry.
VERDICT: The Chocorua by Minus33 looks and feels great with a casual style and slim fit. A point worth mentioning is that Minus33 caters to all-sized people, from short and lean to big and tall, so size won’t be an issue, even if you have lumberjack arms. Comfortable and warm with fast drying and moisture-wicking abilities, the Chocorua is an all-around workhorse with good value for money.
Smartwool Merino 250 Base Layer Crew
- Material: 250 Midweight, 100% Merino Wool
- Weight: 255 g / 9 oz
The Smartwool Merino 250 Base Layer Crew uses 100% merino wool for their best-selling and warmest base layer to date. With an updated design to give you a better fit and improved comfort while carrying a backpack, the chafe-free seam construction feels great against the skin. The form-fit cut looks very modern and not at all like long underwear, following the contours of the body with a stretchy interlocking knit fabrication.
One amazing property of Smartwool merino wool is that even though it is often very thin and lightweight, it does a fantastic job of blocking the sun’s harmful UV rays.
VERDICT: The Smartwool 250 Mid Crew is rated at UPF 50+ for those clear blue sky days but also manages to keep you warm on the coldest of days or in the middle of the night. Flatlock seam construction and shoulder panels on the top are well thought out, and avoid rubbing and chafing from backpacks or climbing gear.
MERIWOOL 100% Merino Wool Midweight Long Sleeve Thermal Shirt
- Material: 100% New Zealand Merino Wool
- Weight: 299 g / 10.55 oz
The MERIWOOL base layer top is made from 100% New Zealand Merino Wool using only the best raw materials to provide quality from start to finish.
The lightweight 250 merino feels cool on a hot day and traps in warmth like nothing else on a cold day. Even if you end up sweating in this shirt, it never feels wet and magically never smells, even if my pits do! MERIWOOL is a well-known producer of reliable outdoor gear made from merino wool, and so this is a brand you can trust.
The thumb holes allow you to slip the cuffs over your knuckles in the biting wind without gloves, or if you do have gloves on then you can keep your sleeves tucked away so that your wrists stay covered. Highly functional and well-made, the MERIWOOL Long Sleeve Merino Shirt is perfect for hiking, fishing, hunting, and all general outdoor work. This an excellent choice if you are on a budget, as these are very reasonably priced.
IceBreaker 260 ZONE Merino Wool Base Layer
- Material: 200 Lightweight, 96% Merino wool, 4% LYCRA (Mesh Panels: 85% Merino wool, 14% Nylon, 1% LYCRA)
- Weight: Medium = 250 g / 8.82 oz
The IceBreaker 260 ZONE Merino Wool Base Layer is an excellent example of new meets old. With a blend of 96% merino wool and 4% LYCRA, you get all the benefits of merino wool but with added stretchiness and contour fitting. Strategically placed merino blend meshing for high-performance ventilation and gusseted side panels for improved ease of movement, the BodyfitZONE is great for extreme and high-intensity sports.
The slim-fitting design doesn’t feel baggy at all, and the added synthetic materials help keep its shape. This is ideal for use as a pure base layer on steep climbs and sports training, where keeping a slim profile helps give you an edge.
The thumb holes are a nice touch that, in my opinion, should be on every base layer, and the core-spun fabric and flatlock seams help prevent chafing and enhance durability. Even though it isn’t 100% all-natural, the Icebreaker BodyfitZONE is still one of the best merino wool base layers for outdoor adventures.
Woolly Clothing Merino Wool Long Sleeve V-Neck Shirt
- Material: 100% Australian Merino wool
- Weight: 300 g / 10.6 oz
The Woolly Clothing Merino Wool Long Sleeve V-Neck Shirt is a toastie warm base layer made from 100% New ZealandAustralian Wool. Of all the merino shirt base layers in this guide, I feel like this has one of the better fits and looks great as a casual shirt. It doesn’t feel too tight and is loose enough to be worn over a t-shirt or as a base layer without hugging your figure too tight.
The moisture-repelling fibers wick any sweat away from your body to keep you feeling dry and comfortable and don’t hold any odors. The shirt is very low-key, with no interior labels and just a small tag at the bottom left, which is nice and subtle. It is not uncommon to spot somebody else wearing a Wooly Clothing base layer in hostels or mountain huts when backpacking around the world. Well-trusted in the outdoor community and a solid piece of kit that will last a long time, we highly recommend this merino thermal top.
BaseLayer Mechanics Merino Wool Long Sleeve Crewneck Half-Zip
- Material: 100% Merino Wool
- Weight: Large = 295 g / 10.4 oz
The BaseLayer Mechanics Merino Half-Zip midweight merino wool base layer is made from 100% Merino wool and is silky soft and comfortable to wear on its own. Hard-wearing and super soft, the Baselayer Mechanics merino top will keep you warm with maximum breathability.
No matter how much you sweat in this thing, it simply just does not stop performing and keeps good insulation even when wet. The high-rise collar keeps your neck extra warm when fully zipped up and really helps to trap all your body heat in when it’s cold.
High-performance wool with flatlock seams and underarm gussets means the fabric doesn’t chafe, and you have total freedom of movement. You can wear it hard and throw it in the washer/dryer without worrying about shrinkage. Wash it with all your other clothes. You can wear this shirt for a week or more, and it still won’t smell because the merino wool is naturally odor resistant. Really cool wool base layer for the outdoors and for sleeping in and is slightly lighter than other thicker-weight tops.
Minus33 Ticonderoga Lightweight Crew Merino Wool Base Layer
- Material: 170 Lightweight, 100% Merino Wool
- Weight: Large = 208 g / 7.4 oz
Like many of Minus33’s products, the Ticonderoga is named after a piece of mountain history. Fort Ticonderoga is nestled in the Adirondack mountains and in history, has mastered the trade and travel in the region. The Lightweight Ticonderoga Merino wool base layer provides a fine layer of warmth underneath the close-fitting fabric.
When you couple this with standard layers over the top of the Ticonderoga, you feel totally insulated and flexible. The fit is nice and snug, not too tight and not too baggy, so you can even wear it as your only layer in summer. Some nice bright-colored base layers instead of the standard black or gray.
RAB Forge Long-Sleeve Merino Wool Tee
- Material: 53% polyester (32% recycled), 47% merino wool
- Weight: :169 g / 5.9 oz
The RAB Forge Long-Sleeve Merino Wool Tee uses a blend of 47% superfine Merino wool and 47% polyester which gives the top some added durability and speeds up drying time. Striped interlocking fabric construction has a luxurious feel, and the flatlock seams reduce rubbing with a backpack.
While I do try and buy 100% merino products when given a choice, I do not mind a merino wool blend if the end product does its job. The RAB Forge Long-Sleeve Merino Wool Tee has a slim fit, looks great on its own, and keeps you warm with other layers, but it is not the best value for money, in my opinion.
Helly-Hansen LIFA Merino Lightweight Crew Baselayer
- Material: 215 Midweight, 57% Merino wool, 43% Polypropylene
- Weight: 200 g / 7.05 oz
The Helly-Hansen LIFA Merino Lightweight Crew Baselayer has the lowest percentage of wool content on this list of the Best Merino Base Layers but still earns its spot due to its reputation.
Made from just 57% merino wool and 43% LIFA fiber technology, you get a super smooth and soft material that feels light and flexible with a lean fit. The combination of fabrics supposedly gives it superior insulating and wicking properties, but I suspect this is mostly thanks to the Merino wool content. Overall a better than the average base layer that feels silky smooth and does a good job of regulating your temperature.
Why Do I Need Base Layers?
Base layers are an excellent way to add warmth without adding bulk or making you feel too hot. Whether you are out there exploring mountain ranges or are nestled up in a snow-capped log cabin, keeping warm is a necessity that can be even more urgent than water in some places. Layering up is the best way to stay warm as well as control your body temperature when engaging in physical activities.
Removing layers when you are hot is almost as important as putting them on when you are cold, so having many thin layers is always better than a few really warm layers.
Base Layers are worn next to the skin and are designed to trap warm air against the body when coupled with more layers. Base layers should be light and flexible so as not to restrict movement, as well as feel comfortable against the skin, even when wet. Worn underneath your regular or other specialist clothing, base layers are often very thin and stretchy, so you barely even notice you have them on.
What Size Base Layer to Get?
The Best Merino Wool Base Layers should be worn right next to the skin, and so should be as slim fitting as possible. The closer the base layer is to your skin, the more effectively the fabric can trap a warm pocket of air. Having a tight-fitting base layer only becomes a problem if it feels uncomfortable and restrictive.
If you are worried about sizing, merino wool is super stretchy and allows for generous body types. Even if you plan on wearing two base layers to compensate for extreme cold, as you would any t-shirt or underwear size.
As well as your typical long sleeve top and long-john leggings, you can also get short sleeve base layers and 3/4 length leggings if that is more your style. Short sleeve merino shirts make excellent vests for everyday wear and especially if you work in cold office blocks (we’ve all been there). For most outdoor activities and everyday use, I would recommend buying lightweight to midweight garments and only going for heavyweight if you are expecting below-freezing temperatures.
How Much Difference Does the Material Make?
When you are choosing the material that will be next to your skin for hour upon hour of sweaty hiking or climbing, then you need to be sure it is going to be comfortable.
Synthetic fibers might feel soft when you try them on in shops, but how well they perform in extremes and when soaking wet is another thing entirely.
Natural and synthetic blends are ok, and having some merino wool is better than no merino wool, but I personally prefer to wear the Best 100% Merino Wool Base Layers.
The Benefits of Merino Wool for Base Layers
There are lots and lots of benefits to choosing 100% merino wool over other synthetic or natural fabrics, but to name just a few, here is a shortlist.
- Warm when it’s cold
- Cool when it’s warm
- Odor resistant
- Super soft and stretchy
- Machine washable and dryable
Merino wool is an excellent material for base layers because any type of clothing you wear next to your skin should possess the qualities listed above.
If you sweat, merino base layers wick the moisture away and don’t hold onto body odors. If you get cold easily, the merino will actually thermoregulate your body temperature to make sure you stay warm enough if you are going to be exerting yourself. Then your top needs to be stretchy and breathable so that you don’t feel restricted.
And finally, if you are going to be wearing your merino top outdoors, then you will need to wash it frequently, which merino wool can handle.
- Related Article: 11 Best Women’s Base Layer Tops
Thanks for reading the Top 10 Best Merino Wool Base Layers For Staying Warm Outdoors Without Overheating