Four teens huddle together while playing in the snow, and wearing their warm winter layers!

Let’s talk about the best base layers for outdoor kids! Kids’ thermal underwear is essential in keeping them warm and happy when embarking on winter adventures. Knowing the best base layer for kids – from infants to teens – is the first step to enjoying time outside this winter.

Base layers (or thermal underwear) wick moisture away from the skin – keeping kids warm and dry. The best options are form-fitting. While it is tempting to size up when buying for kids to make them last longer, this layer should be true to size. Fabrics like synthetics (polyester or nylon) or Merino wool are best. 

From experience, we can tell you kids (and adults alike) get cold very quickly without their thermal base layer, making adventures uncomfortable and potentially dangerous. Whether you are searching for the best kid’s ski base layer or simply want to play outside in the snow together, this article will help you identify the best base layer options for your kids. Keep reading to learn more about how to layer kid’s clothes for winter! 


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Why Base Layers Are So Important

A young child skis along a snowy trail in the mountains.

Braving the chilly embrace of winter calls for a strategic layering plan – especially with kids. Having warm winter clothes for outdoor kids is crucial for fun family adventures all season long. Consider kid’s thermal underwear as trusty adventure companions, striking that perfect balance between warmth and flexibility. It’s easier to shed a layer if kids get too hot, but adding one mid-adventure is challenging.

Each layer plays a crucial role in shielding and regulating body temperature during frosty exploration. Understanding these functions empowers you to mix and match brands and styles tailored to your family’s winter pursuits—be it hiking, snowshoeing, skiing, or snowy playdates. Our layering suggestions cater to many activities, ensuring a great outdoor experience for the whole family. For more extreme adventures like winter backcountry camping, adapt accordingly to your unique climate. In this article, we will cover the best base layers for kids. If you want to learn more about how to layer kids’ clothes for winter, read our article on Winter Layering for Kids.

Wool or Synthetic Base Layers?

A mom and her young son snowboard in Lake Tahoe., one of the best winter vacations for families.
Photo Courtesy: Ashlee Cross

Are the best base layers for kids Merino wool or synthetic? The answer depends on a few different factors. First, consider your kid’s comfort, your budget, and your family’s typical outdoor activity. Some kids may naturally prefer one fabric over another. Here are some ways that Merino and synthetic base layers differ for kids:

  • Synthetic: Synthetic fabrics such as polyester, nylon, or recycled polyester for base layers are cost-effective and dry fast due to low water absorption. However, remember that they can trap odors, especially after repeated use without washing. If odor retention concerns you, look for options treated with antimicrobial properties.
  • Merino Wool: Merino wool is widely acknowledged as the best option for base layers from babies to teens. Although it tends to be pricier, many families see the value in the investment. Merino wool boasts excellent breathability, optimal temperature regulation, and durability. Plus, it’s naturally odor-resistant.

Then, you may have noticed that base layers and wool socks come in different weights. Each brand should list its temperature rating, but here is a very basic review to help get you started in choosing the best options for your family:

  • Lightweight: Moderate to cool temps (fall, early winter, spring in most of Canada and the northern United States)
  • Midweight: Cold temps (early winter/end of winter in most of Canada and the northern United States)
  • Heavyweight: Below-freezing temps (the heart of winter in most of Canada and the northern United States)

Fabrics to Avoid

Before covering the best thermal wear for kids, we want to highlight some fabrics to avoid. Avoid fabrics like cotton, jeans, and tight, non-breathable layers. These materials can trap moisture and compromise warmth. Alternatively, they can cause discomfort or make movement a challenge for kids. Instead, focus on the Merino base layers, mixed layers, and synthetic layers that come next.

Best Merino Base Layers for Kids

If you’re looking for the best Merino base layers for kids, these are our favorite brands from infants to teens. From hiking along snowy trails to hitting the slopes, these kids’ thermal underwear layers will keep them cozy and having fun all day long!


Product shot of bright yellow base layers for kids from Iksplor.
Photo Courtesy: Iksplor

Iksplor Merino wool baselayers combine comfort and functionality for year-round adventures. In fact, these Merino base layers for kids provide natural insulation, regulating body temperature in various climates. Plus, adventure families love them for their soft and breathable fabric – and the ability to have matching family colours! Not to mention, the vibrant colours add a playful touch! Kids’ layers come in sets (sizes newborn to 12y), while women’s base layers come as single pieces (sizes XS to XL). 

In addition to base layers, Iksplor offers a variety of other adventure clothing, including joggers, nursing tops, beanies, socks, and more. Undoubtedly, they are an excellent option for those looking for toddler base layers and youth base layer sets!

Use our discount code to receive 15% off: kidswhoexplore2023

Simply Merino Base Layers

Four product shots, side by side, of Simply Merino base layers for kids and women.
Photo Courtesy: Simply Merino

Made in Canada, Simply Merino is one of our favorite base layer options for babies, kids, and adults. In fact, they offer some of the most diverse options for base layers, from infant gowns and onesies to pajamas, dresses, and more. Sizing includes everything from newborns to adult XXXL (men’s and women’s sizes), making them one of the most sizing-inclusive options on this list. Each item is made using 100% Australian Merino wool. Plus, each item is available in various colors, from earth tones to more robust palettes.

In addition to base layers, Simply Merino also offers beanies, neck warmers, pilot hats, bibs, and more.


A colorful base layer shirt for kids from Smartwool.
Photo Courtesy: Smartwool

Smartwool’s base layers for kids are made of 100% Merino wool. Plus, these Merino base layers for kids are also a bit thicker than other options on this list, providing a softer feel and lasting longer. As such, they are an excellent option for families looking for ski base layers for kids. Kids sizes come in XXS – XL (recommended for ages 3 – 14). The tops and bottoms are sold separately, so you can mix and match as needed. For example, this makes them a convenient option if you need more bottoms than tops (or vice versa).

As some of the best base layers for kids, various coordinating patterns are also available for hats, neck gaiters, adult base layers, and headbands. Plus, men’s and women’s sizes come in XS – XXL (some women’s plus sizes are also available up to 3X).


Three side by side product, lifestyle shots of Reima thermal underwear for kids.

Reima offers some of the best Merino base layers for kids, from infants to teens. They offer sizing from 12 – 18 months to teens. Reima has a reputation for being super soft, thick, and very warm and toasty! They also offer sets like the Baby, Toddler & Kids Wool Base Layer Set – Taitoa and the Merino Wool Thermal Base Layer Set – Taival. They are made with responsibly sourced wool.

Alternatively, they also offer youth base layer sets made with mixed and synthetic fabrics. These budget-friendly alternatives give you the same high-quality comfort that Reima is known for without breaking the bank.

Wee Woolies

A vibrantly colored Wee Woolies base layer set for toddlers.
Photo Courtesy: Wee Woolies

Looking for bright and beautiful kid’s thermal underwear? You’re going to love Wee Woolies! Fashioned in Canada, they offer Merino base layer sets for infants to kids. Wee Woolies are lightweight, breathable, and 100% natural. Plus, most families find them super soft! Sets come in sizes 0 – 3 months to 6y, plus you can get single pieces up to size 12y. These midweight base layers are perfect for year-round adventures from the backyard to the backcountry.

They also offer dresses, blankets, sleepers, shorts, beanies, and more for babies, toddlers, and kids.

Chasing Windmills

A young girl jumps on a bed wearing base layers from Chasing Windmills.
Photo Courtesy: Chasing Windmills

Chasing Windmills, a Denver-based direct-to-consumer brand, produces base layers with midweight Merino wool. These layers are widely recognized and beloved for their softness and sustainable sourcing. They feature reinforced knees in various colors and straightforward patterns for enhanced durability. They offer sizes 3 – 6 months – 12y for kids’ thermal wear, and women’s sizes XS – XXL.

Then in addition to base layers for infants to women’s sizes, they also offer trousers, skirts, beanies, hats, short sets, hoodies and pullovers, and more for kids.

Best Synthetic/Mixed Base Layers for Kids

If you prefer synthetic or mixed base layers for kids, we have also selected the top options for those! These options tend to be more budget-friendly, but keep kids just as warm!

Jan & Jul

A young girl takes a walk in fall leaves where a base layer set from Jan & Jul.
Photo Courtesy: Jan & Jul

One of the most budget-friendly options on this list, Jan & Jul is another excellent choice for families searching for the best base layers for kids (sizes 2T – 12Y)! While they don’t offer youth base layer sets, each piece is priced to keep exploring the outdoors comfortable and affordable. Families find Jan & Jul base layers thick, cozy, and warm. They are ideal for everyday wear and can function as both an outfit and a thermal layer. Since these thermals are a bit thicker than some alternatives, they are suitable for kids who tend to be more active and challenging on their clothes.

Plus, Jan & Jul offers various other outdoor clothing, making them a great one-stop shop for seasonal outerwear, footwear, and accessories.

Use our discount code: kidswhoexplore10


Two long-sleeve base layer tops from Patagonia, side by side.
Photo Courtesy: Patagonia

Patagonia offers versatile thermal underwear for babies and kids made of 100% recycled polyester fabric (with odor control). They are lightweight and come in different colors and patterns. For infant and toddler base layers (sizes 3-6 months to 5T), check out the Baby Capilene® Midweight Henley. Try the Kids’ Capilene® Midweight line for older kids, which offers bottoms and tops (sizes XS – XXL). Pants and shirts are sold separately; they do not provide sets in any size.

Lands End

A shirt and two bottoms from Lands End, some of the best layers for kids this winter.
Photo Courtesy: Lands End

Lands End is an excellent choice if you’re looking for a great, affordable base layer for when kids are growing fast. While they don’t offer youth base layer sets, you can mix and match the many colors and patterns they have to highlight your child’s color preferences and personality! Kids’ sizes are available from XXS to XXL. These synthetic layers are made with 90% polyester/10% elastane, thumb loops, flat-lock seems, and an antimicrobial finish to keep them fresh. These layers are only guaranteed up to 30 washes, so if you are a very active family, they may not be the best fit.

They also offer men’s sizes S – XXL, women’s sizes XS-XL, and women’s plus sizes from 1X – 3X, making them another one of the most size-inclusive options on this list.

REI Co-op Lightweight Crew Base Layer

A base layer top in green from REI.

If you need a durable, lightweight base layer, REI Co-op Lightweight Crew Base Layer is an excellent all-season, all-sport option for kids. As a lightweight layer, they are a perfect option for kids who constantly complain about being warm or too hot. They are created with a soft recycled polyester/spandex blend fabric that wicks moisture and dries quickly. Plus, they offer UPF 50 sun protection. The toddler base layers come in sizes 12 months – 4T, while the kid’s sizes range from XXS to XL (recommended ages 4 – 16). Bottoms and tops are sold separately, but both are very affordable. 

Happy Trails!

A parent pulls two kids on skis during the winter.

We hope this article on the best base layers for kids is helpful in preparing for your upcoming winter adventures. And, stocking up on warm winter clothes for outdoor kids. Whether you are looking for ski base layers for simple thermal wear for kids to keep them warm and outside this season, we know there is a brand or two on this list that’s right for you. We wish you and your kids a winter season filled with adventure, exploration, and fun!

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