Best Thermal Underwear Bottoms for Boys of 2026

The Merino.tech Kids Wool Pants offer a cozy and practical base layer for your child. Made from 100% superfine merino wool, these thermal pants provide soft comfort all day without the irritation or overheating common in cotton underwear. Their natural moisture-wicking ability keeps your child dry by drawing sweat away from the skin, while the wool’s odor-resistant quality helps maintain freshness during active play. Plus, these pants are breathable and help regulate your child’s body temperature year-round, making them a reliable choice for any season. They’re also easy to care for by hand washing and laying flat to dry.

The Hot Chillys Youth Thermal Tights are designed to keep your child warm and comfortable during cold weather activities. These midweight base layer pants provide cozy insulation without bulk, making it easier for your child to move freely. They feature special moisture-wicking fibers that pull sweat away from the skin, helping your child stay dry and comfortable even during active play. The tights also have a snug, stretchy fit that moves with your child and offers UPF 30 sun protection. With a warmth rating of 8 out of 10, these tights are ideal for chilly days when your child needs reliable warmth and breathability.

The MERIWOOL Kids Thermal Bottoms are perfect for keeping your child warm and comfortable during cold weather. Made from 100% Merino wool, these lightweight bottoms fit snugly against the skin, offering excellent temperature control and moisture-wicking to keep your child dry and cozy. Whether worn alone or as a base layer, they resist odors and stay fresh longer, which means fewer washes and less packing for trips. Designed for active kids, they are soft and itch-free, ensuring no irritation during play or sports. Plus, the eco-friendly fabric ensures durability and comfort for your little ones.

The Iguana Merino Wool Pants are made from 100% super fine merino wool, offering a soft and stretchy fit that keeps you warm without feeling bulky—perfect for skiing or everyday wear. Thanks to the fine fibers, these pants are gentle on your skin, so you won't experience any itchiness or irritation. They also help manage sweat by moving moisture away from your body, keeping you dry and comfortable. Plus, their natural properties prevent static cling, so you can wear them without any annoying static shocks or clinginess. These pants are designed to make your cold-weather activities more comfortable and enjoyable.

The TELALEO Boys Thermal Leggings are designed to keep your child warm and comfortable during cold weather activities. Made with a blend of polyester and spandex, these leggings stretch to fit well while providing flexibility. The soft, brushed fleece lining inside offers extra warmth, making them ideal for chilly days. Thanks to moisture-wicking technology, these leggings help keep sweat away from the skin, ensuring your boy stays dry and comfortable. Additionally, the smooth flat seams reduce irritation and chafing, so your child can stay active with ease and durability.

The DEVOPS Thermal Compression Tights are designed to keep you warm and comfortable during any activity. Made with a soft fleece lining, these tights feel gentle against your skin, providing cozy warmth. They stretch easily thanks to added spandex, allowing you to move freely without losing their shape. The close fit helps trap your body heat, making sure you stay warm outdoors or during indoor sports. Whether you're playing outside or relaxing indoors, these tights offer versatile performance and comfort for all your active days.

The SmartWool Kid Thermal Bottoms are designed to fit close to your child’s body, providing a comfortable and snug feel that moves with them. Made from soft Merino wool with an interlock knit, these bottoms help regulate temperature and keep your child dry by allowing breathability. You’ll also appreciate the natural odor resistance of Merino wool, keeping the bottoms fresh even after active play. The elastic waistband, covered in Merino wool, adds extra comfort without digging in. Plus, flatlock seams reduce chafing, so your child can stay comfortable all day long, whether indoors or out in the cold.

The Woolino Kids Merino Base offers your child warmth and comfort thanks to its 100% super soft merino wool fabric. This natural material keeps your little one cozy by regulating body temperature, wicking away moisture, and resisting odors, making it perfect for active kids. Designed for all-day and year-round wear, it stays warm even when damp, ensuring your child stays comfortable during chilly mornings or cold nights. The growth-friendly design includes extended cuffs, allowing the top to fit longer across seasons. Plus, the set is certified safe and made with sustainable, mulesing-free wool, giving you peace of mind about quality and safety.

The MANCYFIT Boys Thermal Leggings are designed to keep your child warm and comfortable during cold weather. Made with a soft blend of polyester and spandex, these leggings provide warmth without feeling heavy or bulky. They also help wick away moisture, so your child stays dry and cozy even during active outdoor play. The stretchy fabric allows for easy movement, giving your child full flexibility and comfort under their clothes. As a perfect base layer, these thermal leggings fit well under jeans or sportswear, making them a versatile addition to your kid’s winter wardrobe.

The JAN & JUL Base Layer Pants offer a soft and stretchy fit that your child will enjoy wearing both indoors and outdoors. Made from a durable polyester and spandex blend, these pants provide flexibility and comfort for active toddlers. They are designed to keep your little one warm during chilly days, making them perfect for school or outdoor activities like skiing. The fabric also helps manage moisture, preventing sweat buildup so your child stays dry and comfortable. With a roomy yet slim fit and wide ankle cuffs, these pants are great for everyday wear and layering in cold weather.