Your backpacking trip’s success often starts with the first layer you put on. A high-quality base layer is the unsung hero of any hiking kit, responsible for managing moisture, regulating temperature, and keeping you comfortable when the weather turns. Choosing the right one can mean the difference between a memorable adventure and a miserable slog.
With options ranging from luxurious merino wool to high-tech synthetics, the perfect base layer for your needs is out there. To simplify your search, we’ve compiled a list of top-performing options for 2025. This roundup focuses on durability, functionality, and comfort to help you stay dry and warm on the trail, no matter what your itinerary holds.
Our Top Picks for Hiking Base Layers
- Smartwool Men’s Classic All-Season Merino Base Layer
- Smartwool Men’s Merino 250 Baselayer Crew
- Icebreaker Merino Men’s 200 Oasis Ls Crewe
- Carhartt Men’s Base Force® Midweight Base Layer
- Smartwool Merino 250 Base Layer Crew
- Icebreaker Oasis Long Sleeve Crewe
- Under Armour ColdGear Authentic Base Layer Tights
- REI Co-op Midweight Base Layer Top
Smartwool Men’s Classic All-Season Merino Base Layer
For a versatile base layer that handles a wide range of conditions, the Smartwool Classic All-Season is a fantastic choice. Its blend of 88% Merino Wool and 12% Nylon offers the best of both worlds: the natural odor resistance and temperature regulation of wool, with the added durability and stretch of nylon. This makes it a reliable partner for everything from cool morning starts to strenuous ascents.
The fabric is soft against the skin and effectively wicks moisture to keep you dry. It’s a true three-season workhorse that provides consistent comfort without bulk, making it easy to layer under a shell or fleece when needed.
Smartwool Men’s Merino 250 Baselayer Crew
When the temperature drops, the Smartwool Merino 250 Baselayer is designed to deliver superior warmth. This is a dedicated cold-weather base layer built with a 100% Merino wool construction in a midweight fabric. It excels at moving moisture away from your skin to keep you warm and dry during winter hikes and backpacking trips.
The updated slim fit is designed for outdoor adventuring, offering a streamlined silhouette without restricting movement through the arms and chest. This thermal layer is a crucial piece for anyone facing freezing conditions, providing reliable insulation that breathes to prevent overheating during exertion.
Icebreaker Merino Men’s 200 Oasis Ls Crewe
The Icebreaker Oasis Long Sleeve Crewe is a benchmark for merino wool performance. Made from 100% Merino wool, this base layer is known for its exceptional softness and natural ability to manage body temperature. The 200-weight fabric offers a balance of warmth and breathability, making it suitable for active use in cool to cold weather.
Icebreaker’s commitment to quality is evident in the garment’s construction and feel. It resists odors naturally, allowing for multiple wears on a long trip, and provides consistent comfort next to your skin. It’s a reliable, high-performance option for backpackers who prioritize natural materials.
Carhartt Men’s Base Force® Midweight Base Layer
Built for demanding use, the Carhartt Base Force® Midweight Base Layer brings rugged durability to the trail. Its Force technology is engineered to wick sweat and dry quickly, helping to maintain a comfortable body temperature during intense activity. The FastDry property and odor resistance make it a practical choice for multi-day trips.
Thoughtful design elements like strategically placed flatlock seams reduce chafing, while the concealed thumb loops and locker loops add functionality. This base layer is a solid pick for backpackers who need a tough, no-nonsense layer that can withstand heavy use and abrasive gear.
Smartwool Merino 250 Base Layer Crew
Another iteration of the popular 250 series, this Smartwool crew offers proven cold-weather performance. The heavyweight 100% Merino wool fabric provides substantial insulation for the coldest backpacking adventures. Its primary function is to retain body heat while actively moving moisture to the outer layers, where it can evaporate.
This type of base layer is essential for winter camping and alpine environments where maintaining a stable core temperature is critical. The natural properties of merino wool ensure you stay warm even if the layer gets damp, offering a significant safety advantage in volatile conditions.
Icebreaker Oasis Long Sleeve Crewe
The Icebreaker Oasis line is celebrated for its pure, wear-anywhere comfort. As a midweight option, it serves as an excellent all-around base layer for three-season backpacking. The 100% Merino wool construction provides reliable temperature regulation, keeping you cool when you’re active and warm when you’re at rest.
Its versatility extends to its odor resistance, which is a major benefit for minimizing pack weight and laundry on extended journeys. For those who prefer the feel and performance of pure merino wool without a blended fabric, the Oasis Crewe is a top-tier selection.
Under Armour ColdGear Authentic Base Layer Tights
For your lower body, the Under Armour ColdGear Authentic Tights provide a snug, protective layer against the cold. These synthetic tights are engineered with a brushed, midweight fabric that traps body heat while effectively wicking sweat to keep your skin dry.
The form-fitting design minimizes air pockets and reduces bulk under your hiking pants, allowing for a full range of motion. This is an ideal base layer for your legs during cold-weather hikes, offering warmth without the weight of heavy fabrics.
REI Co-op Midweight Base Layer Top
The REI Co-op Midweight Base Layer Top represents excellent value from a trusted outdoor retailer. Designed to perform in cool to cold conditions, it effectively manages moisture and provides consistent insulation. This layer is a great option for backpackers who want reliable performance without a premium price tag.
It’s constructed with durability and comfort in mind, making it a practical choice for both weekend trips and longer expeditions. As a core piece from REI’s own line, it benefits from extensive field testing and is built to meet the demands of fellow outdoor enthusiasts.
Buying Guide: How to Choose Your Hiking Base Layers for Backpacking
Choosing the right hiking base layers for backpacking is one of the most critical gear decisions you’ll make. Get it wrong, and you’re in for a miserable, potentially dangerous trip. Get it right, and you’ll stay comfortable across a huge range of conditions. The core principle is moisture management: moving sweat away from your skin to keep you dry and warm. Let’s break down what you need to look for.
First, let’s talk fabric. You’ll primarily see three types: merino wool, synthetic, and blends. Merino wool is my personal favorite for most conditions. It’s naturally odor-resistant, meaning you can wear it for multiple days on the trail, and it regulates temperature beautifully, keeping you warm when it’s cold and cool when it’s hot. It also retains some insulating properties even when wet. The downside is it’s less durable than synthetics and can be more expensive.
Synthetic fabrics, like polyester and nylon, are the workhorses of the base layer world. They excel at wicking moisture away from your skin extremely quickly, making them ideal for high-intensity activities in cold weather where sweat buildup can lead to rapid cooling. They are also very durable and often more affordable than merino. The major drawback? They tend to hold onto body odor much more than wool.
Many of the best hiking base layers for backpacking in 2025 are actually blends of merino wool and synthetic materials. This gives you the best of both worlds: the odor resistance and comfort of wool with the durability, faster drying time, and lower cost of synthetics. A common blend is around 60% merino and 40% polyester.
Next, consider the weight of the fabric. Base layers typically come in light-, mid-, and expedition-weight categories. Lightweight is best for summer hiking, high-output activities, or as a first layer in a serious layering system. Midweight is your versatile three-season option, providing a great balance of warmth and breathability for most backpacking trips. Expedition-weight is for serious cold, winter mountaineering, or static camp use where maximum warmth is the priority.
Finally, pay attention to the fit. Your base layer should have a snug, almost skin-tight fit. This is called a “technical fit.” It needs to be close to your skin to effectively wick moisture. If it’s baggy, that moisture will cool on the fabric instead of being moved away, making you cold. Look for flatlock seams that lie flat against the skin to prevent chafing under your backpack straps. Features like a longer torso and thumbholes can also add valuable comfort and protection from the elements.
FAQ
Can I just wear a cotton t-shirt as a base layer?
Absolutely not. This is the number one rule of hiking and backpacking: cotton kills. Cotton absorbs moisture and holds it directly against your skin. When you sweat or get caught in the rain, a cotton shirt will stay wet, rapidly drawing heat away from your body and leading to hypothermia, even in mildly cool conditions. Always choose a moisture-wicking material like merino wool or synthetics for your hiking base layers for backpacking.
How often should I wash my merino wool base layer?
One of the superpowers of merino wool is its natural odor resistance. You can often get 3-5 days of wear out of a merino top before it needs a wash, which is a huge advantage on multi-day trips. When you do wash it, use a gentle, wool-specific detergent and cold water. Avoid fabric softeners, as they can clog the wool’s fibers and reduce its wicking ability. Always air dry your merino wool; never put it in a dryer.
Is it worth spending more on a premium brand?
Often, yes. While there are decent budget options, premium brands like Smartwool, Icebreaker, and Patagonia typically use higher-quality wool with longer, finer fibers. This results in a fabric that is softer, less itchy, more durable, and performs better over the long haul. Think of it as an investment in your comfort and safety on the trail. That said, many smaller or direct-to-consumer brands are now offering excellent quality at a more accessible price point.
Do I need different base layers for my top and bottom?
It’s a good idea. Your upper body generates most of your heat and sweat, so you might prefer a lighter weight or more breathable fabric on top. For your legs, a midweight layer is often sufficient for three-season use as your legs don’t sweat as much and are more muscular, generating their own warmth. Many hikers will bring a dedicated sleep top or bottom to change into at camp, keeping their hiking layers separate.
What’s the best base layer for very cold, winter conditions?
For serious cold, a dedicated expedition-weight base layer is your best bet. These are thick, plush fabrics designed for maximum warmth. Some people also opt for a grid-fleece style synthetic base layer, which traps warm air in its grid pattern and is exceptionally good at wicking moisture during high-output activities like snowshoeing or winter hiking. Layering a midweight merino top under a grid-fleece top is a very effective combination for extreme conditions.
How should my base layer fit under my other clothes?
Your base layer should be the tightest layer in your system. It needs to be snug against your skin to effectively pull moisture away. Your mid-layer (like a fleece) will be a bit looser to trap warm air, and your outer shell (rain jacket) will be the loosest to fit over everything else. If your base layer is baggy, it won’t wick properly and will create cold, damp spots. Think of it like a second skin.