10 Best Thermal Underwear Sets 2025 in the United States

The Thermajohn Long Johns Thermal Underwear Set for Men, available in Medium and Navy, is designed to keep you warm and comfortable in cold weather. Made from a blend of 92% Polyester and 8% Spandex, the material is lightweight yet effective in retaining heat. The ultra-soft fleece lining adds an extra layer of comfort, making it suitable for everyday wear or even as pajamas.

The set is breathable and features moisture-wicking properties, which help keep you dry by wicking away sweat and moisture. This is a great feature for active users or those who may wear it for extended periods outdoors. The 4-way stretch material ensures a good fit, allowing freedom of movement without chafing or bunching up. This makes the underwear set versatile for various activities, from lounging to engaging in outdoor sports.

The set is machine washable, making it easy to care for. This thermal underwear set is ideal for anyone needing an extra layer of warmth, especially those who value comfort and flexibility in their clothing.

The Merino.tech Merino Wool Base Layer Men's Set offers a high-quality option for those seeking thermal underwear. It's made from 100% superfine 17.5 micron merino wool, which is known for its softness and comfort, reducing the likelihood of itching or discomfort. The set is midweight at 250 g/m², making it suitable for cooler weather without being overly bulky. Additionally, there's an option to select lightweight or heavyweight versions, which gives flexibility depending on the user's needs.

This set also includes a pair of merino wool hiking socks, adding extra value to the package. The moisture-wicking and odor-resistant properties of merino wool are significant benefits, ensuring that users stay dry and fresh even during prolonged wear. This makes the set ideal for outdoor activities or long days of wear. The breathability of the material helps to regulate body temperature, enhancing comfort throughout different seasons.

Durability might be a concern as the product requires hand washing and air drying to maintain its longevity. This could be inconvenient for some users who prefer machine-washable options. Additionally, although the set is designed to avoid issues like rubbing or bunching, the fit might still vary depending on individual body types. Users who prioritize high-quality, comfortable, and functional thermal underwear will find this set beneficial, especially for moderate to intense outdoor activities.