10 Best Thermal Long Johns 2026 in the United States

The WEERTI Thermal Underwear for Men Long Johns is designed to be a reliable base layer for cold weather. Made from 92% polyester and 8% spandex, the material is lightweight yet offers warmth and comfort. The fleece lining helps in trapping body heat, making it suitable for layering under various types of clothing, from formal wear to casual outfits. The snug fit mimics a second skin, minimizing heat loss, while the 4-way stretch fabric ensures full mobility and flexibility without tearing the seams prematurely.

This is ideal for those who need comfortable yet durable thermal wear for both outdoor activities and lounging at home. The moisture-wicking feature is a significant advantage, keeping sweat at bay and maintaining dryness throughout the day, which is essential for staying comfortable in cold conditions. Additionally, the fabric's odor resistance helps in maintaining freshness after extended wear. However, a potential drawback is the polyester blend, which might not be as breathable as natural fibers like wool. Also, the fit being snug may not be suitable for everyone, particularly those who prefer a looser fit.

Nonetheless, these long johns offer a good balance of warmth, comfort, and functionality for cold weather use.

These Merino Wool Base Layer pants are made from 100% superfine Merino wool, known for its softness and comfort without itchiness, making them great for all-day wear. The midweight fabric (250 g/m²) offers a good balance: warm enough for colder days but breathable enough to prevent overheating. Thanks to the natural moisture-wicking and odor-resistant properties of Merino wool, these long johns help keep you dry and fresh even during active use.

They are designed with a pull-on closure for easy wear and are machine washable, adding convenience. The fit is snug to serve as an effective base layer, with sizing options like X-Large ensuring a comfortable match. An added bonus is the included Merino wool socks, which complement the pants for a full base layer setup.

These pants are ideal if you want natural temperature regulation and odor control in your thermal underwear, especially for hiking or everyday cold weather use. If you prefer synthetic fabrics or require very heavyweight insulation, other options might be more suitable.

The Carhartt Men's Force Midweight Waffle Base Layer Pant is designed with practical features that suit those seeking comfortable, performance-oriented thermal long johns. Made from 100% polyester with Carhartt’s Force technology, these pants excel at moisture-wicking and fast drying, which helps keep you dry during physical activities or cold weather wear. The midweight fabric offers a good balance—not too heavy for layering, yet warm enough for chilly conditions.

Fit-wise, the pants include a brushed elastic waistband with a contoured front and fly for added comfort and convenience. Flatlock seams are thoughtfully placed to minimize chafing, which is a nice plus for all-day wear. Additionally, the fabric fights odor, making these base layers suitable for extended use without smelling unpleasant. The pull-on closure style is simple but effective for easy wearing. One thing to keep in mind is the sizing advice: if you're between sizes, going larger is recommended to ensure a comfortable fit, which suggests the fit might run a bit snug.

These base layer pants are a solid choice for men needing reliable moisture management, comfort, and odor control in moderately cold weather, especially if you want something durable from a recognizable workwear brand.