REI Accessibility Statement
Skip to main content
Skip to Shop REI categories

Shop REI
REI Outlet
Trade-In
Travel
Classes & Events
Expert Advice
Uncommon Path
Membership

My REI Find your store
Sign In
Cart

My Account - Sign in or Register
All Camp & Hike
New arrivals

Sale & Clearance

Save 10% on Co-op Camp Bundles
- Expert Advice
- Classes & Events
All Climb
New Arrivals

Sale & Clearance
- Expert Advice
- Classes & Events
All Cycle
New Arrivals

Sale & Clearance

Brand Spotlight: USWE
All Water
New Arrivals

New at REI: Simms

Brand spotlight: BOTE

Sale & Clearance
- Expert Advice
- Classes & Events
All Run
New Arrivals

Just-released running shoes

All Fitness

Workout clothing

Sale & Clearance
- Expert Advice
- Classes & Events
All Snow
New Arrivals

Sale & Clearance

Snow Gear: Packs, Bags & Racks
- Expert Advice
- Shop Services
All Travel
Trips with Intrepid

New Arrivals

Sale & Clearance
- Expert Advice
All Men
- All Men
- Shoes
  - All Shoes
  - Hiking Shoes
  - Running Shoes
  - Boots
  - Casual Shoes
  - Sneakers
  - Sandals
  - Socks
  - Insoles
- Jackets
- Tops
- Bottoms
  - All Bottoms
  - Pants
  - Shorts
- Underwear
- Swimwear
- Accessories
- Headwear
  - All Headwear
  - Hats
  - Sun Hats
  - Bandanas
  - Neck Gaiters
  - Balaclavas
- Activity Collections
- Big, Tall & Short
  - All Big, Tall & Short
  - Big
  - Tall
  - Short
- Men's Deals
New Arrivals

Sale & Clearance
- Expert Advice
All Women
- All Women
- Shoes
  - All Shoes
  - Hiking Shoes
  - Running Shoes
  - Boots
  - Casual Shoes
  - Sneakers
  - Sandals
  - Socks
  - Insoles
- Jackets
- Tops
- Bottoms
  - All Bottoms
  - Pants
  - Leggings
  - Shorts
- Skirts & Dresses
- Underwear
- Swimwear
- Accessories
  - All Accessories
  - Sunglasses
  - Watches
  - Bags
  - Gloves & Mittens
  - Belts
  - Leg Gaiters
- Headwear
  - All Headwear
  - Hats
  - Sun Hats
  - Bandanas
  - Neck Gaiters
  - Balaclavas
- Activity Collections
- Plus, Petite & Tall
- Women's Deals
New Arrivals

Sale & Clearance
- Expert Advice
All Kids
- All Kids
- Footwear
  - All Footwear
  - Boots
  - Shoes
  - Sandals
  - Socks
- Jackets
- Clothing
- Accessories
- Snow
- Kids' Camp & Hike
- Kids' Cycling
- Strollers
- More
- By Gender & Age
- Kids' Deals
New Arrivals

Sale & Clearance
- Expert Advice
All Deals
Shop all deals

REI Outlet deals

Clothing deals

Footwear deals

Camping deals
All Brands
- All Brands
- Made by REI
- Top Brands
  - Arc'teryx
  - KUHL
  - Black Diamond
  - Garmin
  - HOKA
  - La Sportiva
  - Osprey
  - Patagonia
  - Salomon
  - Smartwool
  - The North Face
  - Thule
- Trending Brands
  - prAna
  - Brooks
  - Cotopaxi
  - Danner
  - Dometic
  - Electra
  - Janji
  - On
  - Snow Peak
  - YETI
  - Thousand
  - Vuori
- Member Favorites
  - Big Agnes
  - Cannondale
  - Darn Tough
  - Fjallraven
  - Exped
  - Gregory
  - Keen
  - Merrell
  - NEMO
  - Oboz
  - Sea to Summit
  - Yakima
Patagonia Deals

The North Face Deals

Deals by Brand

Contact Us

Need some help?

Find answers online any time

message 1 of 3.

Up to 50% off past-season styles from top-rated brands.

message 2 of 3.

Become an REI Co-op Member thru 9/7 and earn a $30 single-use promo card—plus a lifetime of benefits. Terms apply.

message 3 of 3.

Members, earn 15% in Total REI Rewards on eligible full-price purchases with the REI Co-op Mastercard. Terms apply.

message 1 of 2.

Up to 50% off past-season styles from top-rated brands.

message 2 of 2.

Members, earn 15% in Total REI Rewards on eligible full-price purchases with the REI Co-op Mastercard. Terms apply.

Skip to search results

loaded 16 results

REI Co-op
Men's Clothing
Men's Underwear

REI Co-op Merino Wool Men's Underwear

(16 products)

Products (16)

Filter

Store Pickup
Ready within 2 hours
Select a store
ZIP or City, State
Example: 98102 or Taos, NM
Ship to Address (13)
- Deals
- 2XL
- 3XL
- Small
- Medium
- Large
- XL
- Multisport
- Wool
- Wool / Wool Blend
- Yes
- Men's
- Lightweight
- Heavyweight
- Black
- Blue
- Brown
- Gray
- Green
- Red
- 4
- 6
- 28
- 29
- 31
- 32
- Merino 185
- Short Sleeve
- Long Sleeve
- Climate Label Certified
- Fair Trade
- Solid
- T-shirt
- Partial-zip

Remove brand filter:REI Co-op Remove features filter:Merino Wool Clear all

Sort: Best Match

View:

REI Co-opMerino Boxer Briefs - Men's
$39.95
120 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Big
Add Merino Boxer Briefs - Men's to Compare
Top Rated
REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's
$39.93
Save 50%
compared to $79.95
232 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Add Merino 185 Long-Sleeve Base Layer Top - Men's to Compare
Top Rated
REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's
$44.93
Save 50%
compared to $89.95
145 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Add Merino 185 Long-Sleeve Half-Zip Base Layer Top - Men's to Compare
REI Co-opMerino Boxers - Men's
$39.95
87 reviews with an average rating of 4.4 out of 5 stars
Size Type:
Big, Regular
Add Merino Boxers - Men's to Compare
REI Co-opMerino 185 Base Layer Bottoms - Men's
$39.93
Save 50%
compared to $79.95
173 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Add Merino 185 Base Layer Bottoms - Men's to Compare
REI Co-opMerino 185 Base Layer Bottoms - Men's
$84.95
0 reviews
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
Add Merino 185 Base Layer Bottoms - Men's to Compare
Top Rated
REI Co-opHeavyweight Merino Base Layer Bottoms - Men's
$99.95
21 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big, Tall
Add Heavyweight Merino Base Layer Bottoms - Men's to Compare
REI Co-opMerino 185 Long-Sleeve Crew Base Layer Top - Men's
$84.95
0 reviews
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
Add Merino 185 Long-Sleeve Crew Base Layer Top - Men's to Compare
REI Co-opMerino 185 Crew Base Layer Top - Men's
$74.95
0 reviews
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
Add Merino 185 Crew Base Layer Top - Men's to Compare
REI Co-opHeavyweight Merino Base Layer Half-Zip Top - Men's
$104.95
34 reviews with an average rating of 4.3 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big, Tall
Add Heavyweight Merino Base Layer Half-Zip Top - Men's to Compare
Top Rated
REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's Tall Sizes
$44.93
Save 50%
compared to $89.95
17 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Tall
Add Merino 185 Long-Sleeve Half-Zip Base Layer Top - Men's Tall Sizes to Compare
New arrival
REI Co-opMerino 250 Half-Zip Base Layer Top - Men's
$109.95
0 reviews
Underwear Weight:
Heavyweight
Size Type:
Regular, Big, Tall
Add Merino 250 Half-Zip Base Layer Top - Men's to Compare
REI Co-opMerino 185 Half-Zip Base Layer Top - Men's
$89.95
0 reviews
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
Add Merino 185 Half-Zip Base Layer Top - Men's to Compare
REI Co-opHeavyweight Merino Long-Sleeve Base Layer Crew Top - Men's
$99.95
53 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
Add Heavyweight Merino Long-Sleeve Base Layer Crew Top - Men's to Compare
New arrival
REI Co-opMerino 250 Base Layer Bottoms - Men's
$104.95
0 reviews
Underwear Weight:
Heavyweight
Size Type:
Regular, Big, Tall
Add Merino 250 Base Layer Bottoms - Men's to Compare
New arrival
REI Co-opMerino 250 Long-Sleeve Crew Base Layer Top - Men's
$104.95
0 reviews
Underwear Weight:
Heavyweight
Size Type:
Regular, Big, Tall
Add Merino 250 Long-Sleeve Crew Base Layer Top - Men's to Compare

Sort: Best Match

Related Expert Advice articles

Our gear reviewer and REI Co-op Member tester evaluated this four-person camp shelter in windy Wyoming. Here's how it performed.

Read full article: Gear Review: Testing the REI Co-op Westward 4 Tent

Related searches

Base Layers: Deals
KUHL Men's Clothing
Base Layers
Merino Wool Base Layers
Merino Wool Shirts
Men's Base Layers
REI Co-op Tarn Backpacks

Checkout faster

Track your order, shop and save— all in one place

Get the REI app

How are we doing?

on this page.

Sign up for REI emails

Get 15% off one REI Co-op brand item. Details

Email

Error Is your email address correct?

REI Privacy Notice

Thank you for signing up!

Check your inbox for your welcome email. It includes your 15%-off coupon and ways to set preferences.

System Maintenance

The newsletter sign-up system is currently down for maintenance.

Who we are

At REI, we believe that a life outdoors is a life well lived. We've been sharing our passion for the outdoors since 1938.

Become an REI Co-op Member

Anyone can join and everyone belongs. Benefits include great gear offers, special pricing on events and an annual Co-op Member Reward—for life. Join once, enjoy forever.

Take a stand

Outdoor equity, climate action, places we love. Raise your voice in the movement to protect and share life outdoors.

REI Cooperative Action Network

Apply for the REI Co-op® Mastercard®

Earn a $100 REI gift card after your first purchase outside of REI within 60 days from account opening.

Details | Manage your card

REI Co-op Account
Orders & Returns
Gifts
- Outdoor Gift Ideas
- Gift Cards
Offers & Discounts
- Sales & Coupons
- Free Shipping Details
Shopping Tools
Learning & Community
Work with Us
REI Co-op
Customer Service

Find answers online anytime.

See our stores and services.

Mon–Fri, 6am–8pm PT

Sat–Sun, 8am–5pm PT

Get REI apps for shopping & adventure

instagram
Tik Tok
facebook
pinterest
youtube
podcasts

© 2026 Recreational Equipment, Inc. All rights reserved. REI and the REI Co-op logo are trademarks of Recreational Equipment, Inc.

Terms of Use
Privacy Notice
US State Privacy Notice
Consumer Health Data Privacy Policy
Product Recalls
CA Transparency Act
Membership Terms
REI Accessibility Statement