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Mack Weldon is about the fusion between old-school quality and modern day technology. During our brand creation, we discovered Weldon, an early 20th century underwear company in both marketing and product design - very similar to the brand we were creating. We embraced the name, flipped it a bit and made it ours.

It’s all about the fabric and construction. We use Lenzing Modal® (made of 100% natural beechwood) which is anti-microbial (prevents odor), manages moisture and keeps you cool. When blended with cotton it actually creates a softer, more luxurious feel.  Seams are designed to stretch and recover, and we use different materials to keep you comfortable where it counts (18-Hour Jersey, micro pique cool zones, stretch rib between legs).

The 18-Hour Jersey

Our signature blend of long staple cotton, Lenzing Modal and Lycra, is our choice for all undershirts and classic underwear styles. The result? We believe it’s simply the softest most comfortable underwear on the market today. To ensure the least amount of garment shrinkage, the fabric is allowed to rest peacefully, unrolled on the cutting table for 18 hours before cutting and sewing.


Daily Performance Wear

Mack Weldon is designed "for daily wear" but many of our wearers loved how the product performed in the gym and on the court. It's meant to fit close to the body, but never tight or restrictive so it's a good balance of compression and long-term comfort. As for the undershirts, the cotton/modal blend wicks moisture and keeps everything cool on hot days.

So, while not designed specifically to wear for sport, it's nice to know that you can. 


Labels on the Outside

When designing the line, we were inspired by some vintage military issue product that had print on the outside of the garment for easy sorting and identification by the wearer. So there is some purpose there that we thought was unique/relevant. Also, we didn't want the lettering to come between your skin and the soft 18-hour jersey. 

Mack Weldon is designed in New York and our warehouse and fulfillment center is in Massachusetts. 

Our gear is manufactured and sourced in WRAP certified factories across the globe - primarily Thailand and Peru. WRAP is an independent, objective, non-profit team of global social compliance experts dedicated to promoting safe, lawful, humane, and ethical manufacturing around the world through certification and education. The factories are also ISO certified with high quality management systems, ensuring that our products are manufactured in the best way possible to create outstanding results.

You can't really know how great Mack Weldon feels until you try it on, and we're confident you'll agree that it's like nothing else in your drawer. If you disagree, email us at and we'll issue a refund or exchange, your choice. Either way, you keep the underwear and our appreciation for trying it on.

Simply put, you get rewarded every time you shop. The bigger your shopping cart, the more you save on that order. This way you don’t have to wait around for a sale... and we don’t have to bombard you with promotional emails.

  • Spend $100 get 10% off
  • Spend $150 get 15% off
  • Spend $200 get 20% off

Please note that Packs generally have savings built into the price and are thus ineligible towards Savings Meter discounts.

Our product is made in one factory so fit should be accurate and consistent.  Find the style and size you like, it will be just the same next time you order. If you have questions you can email us your measurements along with how you like to wear your T's and underwear at  Otherwise, use the below information to help you select the right size:



T - Shirt

Mack Weldon T’s are Standard Fit ­­– not too loose or too tight. Made to wear on their own, they are designed for comfort. Choose your usual T-shirt size. If you like a more relaxed fit or are between sizes, just go up a size.



Mack Weldon Undershirts have an engineered slim fit­, not tight, but cut close to the body for maximum comfort, movement and shape when worn under a dress shirt or sweater. They are also a bit longer so they stay tucked in.  Choose your usual size. If you are between sizes, please reference the size chart to ensure the right size. 



Our range of Boxer Briefs, Trunks, and Briefs are cut close to the body. Choose your usual size.  If you fall between sizes, please reference the size chart to ensure the right size. 



These are one size fits all.


We accept credit cards backed by the major providers on our website: Visa, Mastercard and American Express. Unfortunately we cannot accept some debit cards. If you are having trouble checking out, please email us at so we can help. Alternative payment through PayPal or over the phone may be available.

Drop us a line at’d love to hear from you and will respond within 24 hours Monday-Friday.

You can also Live Chat with us if you need an immediate answer. We're available Monday-Friday from 11am - 4pm EST, though we're frequently online outside of that time frame. Just visit our Contact Us page and begin a chat in the bottom right hand corner.

XT2™ is a fiber created by combining pure silver with cotton. The silver's natural antimicrobal and anti-odor qualities are woven throughout the entire product. It is not a chemical formula or finish treatment, so it never washes out.

3-7 business days for standard shipping via USPS.

1-3 business days for expedited shipping via FedEx Ground to the East Coast

4-5 business days for expedited shipping via FedEx Ground to the West Coast

Orders marked for Next Day shipping before 1pm EST will arrive the next business day.

Happy customers are the best way to get new customers. If you like your Mack Weldon gear, tell a friend and you'll both earn $10.

It's simple, find your unique referral link within the "My Account" section under "referral credits". An invite will be sent to your friends, and when they click on your link they'll receive $10 off their first purchase. We'll add $10 to your Mack Weldon account that will be automatically applied to your next order.

If you're already signed in, you can find your link HERE

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