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Boys Thermal Underwear

(22 products)

Products (22)

Sort: Best Match

Top Rated
SmartwoolClassic Thermal Merino Base Layer Bottoms - Kids'
$48.73
Save 25%
compared to $65.00
52 reviews with an average rating of 4.7 out of 5 stars
REI OUTLET
SmartwoolClassic Thermal Merino Crew Base Layer Top - Kids'
$44.73
Save 31%
compared to $65.00
5 reviews with an average rating of 3.6 out of 5 stars
REI OUTLET
Top Rated
IcebreakerMerino 260 Tech Thermal Base Layer Leggings - Kids'
$49.73
Save 28%
compared to $70.00
7 reviews with an average rating of 5.0 out of 5 stars
REI OUTLET
SmartwoolClassic Thermal Merino Base Layer Quarter-Zip - Kids'
$51.73
Save 26%
compared to $70.00
0 reviews
REI OUTLET
SmartwoolClassic Thermal Merino Base Layer Hoodie - Kids'
$51.73
Save 31%
compared to $75.00
3 reviews with an average rating of 4.7 out of 5 stars
REI OUTLET
IcebreakerMerino 260 Tech Long-Sleeve Half-Zip Thermal Base Layer Top - Kids'
$52.73
Save 29%
compared to $75.00
4 reviews with an average rating of 4.5 out of 5 stars
REI OUTLET
IcebreakerMerino 200 Sonebula Thermal Base Layer Leggings - Women's
$120.00
10 reviews with an average rating of 4.4 out of 5 stars
Helly HansenLifa Merino Midweight Base Layer Set - Kids'
$69.73
Save 30%
compared to $100.00
2 reviews with an average rating of 4.0 out of 5 stars
REI OUTLET
IcebreakerMerino 200 Oasis Base Layer Leggings - Kids'
$41.93
Save 30%
compared to $60.00
6 reviews with an average rating of 3.8 out of 5 stars
Helly HansenMerino Wool Base Layer Set - Kids'
$75.73
Save 36%
compared to $120.00
0 reviews
REI OUTLET
Icebreaker200 ZoneKnit Thermal Base Layer Leggings - Women's
$109.73
Save 26%
compared to $150.00
4 reviews with an average rating of 4.8 out of 5 stars
REI OUTLET
Icebreaker125 ZoneKnit Merino Thermal Leggings - Men's
$93.73
Save 25%
compared to $125.00
0 reviews
REI OUTLET
SmartwoolThermal Merino Jogger Base Layer Bottoms
$93.73
Save 25%
compared to $125.00
1 reviews with an average rating of 5.0 out of 5 stars
REI OUTLET
Helly HansenLIFA Merino Midweight Base Layer Set - Kids'
$100.00
1 reviews with an average rating of 4.0 out of 5 stars
IcebreakerMerino 200 Oasis Thermal Base Layer Leggings - Women's
$78.73
Save 25%
compared to $105.00
66 reviews with an average rating of 4.4 out of 5 stars
REI OUTLET
Icebreaker200 Oasis 3/4 Base Layer Bottoms - Men's
$95.00
10 reviews with an average rating of 4.4 out of 5 stars
Top Rated
IcebreakerMerino 260 Tech Thermal Base Layer Leggings With Fly - Men's
$93.73
Save 25%
compared to $125.00
35 reviews with an average rating of 4.8 out of 5 stars
REI OUTLET
Top Rated
IcebreakerMerino 200 Oasis Long-Sleeve Base Layer Crew Top - Kids'
$41.93 - $60.00
8 reviews with an average rating of 4.5 out of 5 stars
Top Rated
Icebreaker175 Everyday Base Layer Leggings - Women's
$63.73
Save 25%
compared to $85.00
16 reviews with an average rating of 4.9 out of 5 stars
REI OUTLET
Top Rated
IcebreakerMerino 260 Tech Thermal Base Layer Leggings - Women's
$93.73
Save 25%
compared to $125.00
21 reviews with an average rating of 4.6 out of 5 stars
REI OUTLET
Icebreaker200 Oasis Macro Forms Base Layer Leggings - Women's
$85.73
Save 25%
compared to $115.00
4 reviews with an average rating of 5.0 out of 5 stars
REI OUTLET
Top Rated
SmartwoolClassic Thermal Merino 3/4 Base Layer Bottoms - Men's
$105.00
84 reviews with an average rating of 4.7 out of 5 stars

Sort: Best Match

Related Expert Advice articles

What material is best?

Wool is moisture-wicking and odor-resistant, while synthetic fabrics are more durable and less expensive.

Match the temp to the trek

Lightweight layers are best for moderate to cool temperatures. Midweight layers are best for cold temperatures. Heavyweight layers are best for below-freezing temperatures.

Find your fit

To be able to wick sweat efficiently, your next-to-skin layer needs to actually be next to your skin. A comfortably snug fit everywhere is your goal.

Read full article: How to Choose Base Layers