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Men's Base Layer Tops

(64 products)
Products (64)
Sort: Best Match
  • Sale Ends May 25
    Top Rated
    REI Co-opMidweight Long-Sleeve Base Layer Top - Men's
    $41.19
    Save 25%
    compared to  $54.95
    211 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big, Tall
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's
    $67.39
    Save 25%
    compared to  $89.95
    137 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    REI Co-opLightweight Long-Sleeve Crew Base Layer Top - Men's
    $33.69
    Save 25%
    compared to  $44.95
    41 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big, Tall
    Top Rated
    SmartwoolClassic All-Season Merino Long-Sleeve Base Layer Top - Men's
    $39.83 - $74.99
    Save 25% - 60%
    compared to  $100.00
    106 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMidweight Base Layer Half-Zip Top - Men's
    $44.89
    Save 25%
    compared to  $59.95
    194 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big, Tall
  • Text reads: ‘Anniversary Sale 2026. 25% off’ over a collage of Smartwool long-sleeve shirts and colorful socks.

    Save 25% on all Smartwool clothing

    Top Rated
    SmartwoolClassic Thermal Merino Crew Base Layer Top - Men's
    $49.83 - $93.69
    Save 25% - 60%
    compared to  $125.00
    1539 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's
    $59.89
    Save 25%
    compared to  $79.95
    228 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    SmartwoolIntraknit Thermal Merino Colorblock Crew Base Layer Top - Men's
    $49.83 - $97.49
    Save 25% - 61%
    compared to  $130.00
    12 reviews with an average rating of 4.2 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    REI Co-opMerino 185 Base Layer Top - Men's
    $52.39
    Save 25%
    compared to  $69.95
    60 reviews with an average rating of 4.3 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular
  • Sale Ends May 25
    Top Rated
    REI Co-opLightweight Crew Base Layer Top - Men's
    $26.19
    Save 25%
    compared to  $34.95
    32 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big, Tall
    Top Rated
    SmartwoolClassic Thermal Merino Quarter-Zip Base Layer Top - Men's
    $49.83 - $97.49
    Save 25% - 61%
    compared to  $130.00
    62 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    SmartwoolClassic All-Season Merino T-Shirt - Men's
    $71.19
    Save 25%
    compared to  $95.00
    111 reviews with an average rating of 4.0 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    REI Co-opLightweight Half-Zip Base Layer Top - Men's
    $37.39
    Save 25%
    compared to  $49.95
    24 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    Top Rated
    PatagoniaCapilene Midweight Crew Base Layer Top - Men's
    $89.00
    Add to cart to see price
    93 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    SmartwoolIntraknit Thermal Max Merino Quarter-Zip Base Layer Top - Men's
    $69.83 - $116.19
    Save 25% - 54%
    compared to  $155.00
    0 reviews
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    Top Rated
    REI Co-opHeavyweight Merino Long-Sleeve Base Layer Crew Top - Men's
    $99.95
    50 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Heavyweight
    Size Type:
    Regular, Big
    SmartwoolIntraknit Thermal Merino Crew Base Layer Top - Men's
    $59.83 - $112.49
    Save 25% - 60%
    compared to  $150.00
    209 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's Tall Sizes
    $59.89
    Save 25%
    compared to  $79.95
    11 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Tall
    SmartwoolIntraknit Thermal Merino Base Layer Quarter-Zip Top - Men's
    $59.83 - $104.99
    Save 25% - 57%
    compared to  $140.00
    21 reviews with an average rating of 4.3 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    IcebreakerMerino 200 Oasis Long-Sleeve Crewe Thermal Top - Men's
    $89.99
    Save 25%
    compared to  $120.00
    228 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    SmartwoolClassic All-Season Merino Quarter-Zip Base Layer Top - Men's
    $78.69
    Save 25%
    compared to  $105.00
    11 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    REI Co-opHeavyweight Merino Base Layer Half-Zip Top - Men's
    $104.95
    33 reviews with an average rating of 4.3 out of 5 stars
    Underwear Weight:
    Heavyweight
    Size Type:
    Regular, Big, Tall
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's Tall Sizes
    $67.39
    Save 25%
    compared to  $89.95
    17 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Tall, Big
    Top Rated
    SmartwoolClassic Thermal Merino Crew Base Layer Top - Men's
    $84.73
    Save 26%
    compared to  $115.00
    318 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    REI OUTLET
    Top Rated
    Arc'teryxRho LT Crew Neck Base Layer Top - Men's
    $100.00
    45 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    Top Rated
    SmartwoolClassic Thermal Merino Base Layer Quarter-Zip - Men's
    $89.73
    Save 25%
    compared to  $120.00
    62 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    REI OUTLET
  • Limited time only! The R E I Co-op Mastercard.

    Get $130 in value

    When approved for the REI Co-op Mastercard by May 25, you’ll get $30 in card rewards. Plus, you can earn a $100 REI gift card after your first non-REI purchase within 60 days from account opening. Terms apply.

  • Sale Ends May 25
    Top Rated
    IcebreakerMerino 260 Tech Long-Sleeve Crewe Thermal Top - Men's
    $93.69
    Save 25%
    compared to  $125.00
    80 reviews with an average rating of 4.7 out of 5 stars
    Underwear Weight:
    Heavyweight
    Size Type:
    Regular, Big
    tasc PerformanceElevation Merino T-Shirt - Men's
    $46.73 - $54.73
    Save 30% - 40%
    compared to  $79.00
    56 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Big, Regular
    REI OUTLET
    PatagoniaCapilene Midweight Zip-Neck Base Layer Top - Men's
    $99.00
    Add to cart to see price
    80 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    SmartwoolClassic Thermal Merino Base Layer Hoodie - Men's
    $108.73
    Save 25%
    compared to  $145.00
    3 reviews with an average rating of 5.0 out of 5 stars
    Underwear Weight:
    Midweight
    Size Type:
    Regular, Big
    REI OUTLET
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