Best Thermal Underwear Union Suits for Men of 2025

"I absolutely love these! Being a 5'11 woman, finding long John's that fit has been a challenge. These men's style are perfect with a 34” inseam. The fabric is soft and keeps me warm. I'm definitely buying more!"

"I got this for my husband, and he is really impressed! The material is so soft and it fits true to size. It's not bulky and definitely keeps him warm. Highly recommend!"

"I'm 5'11" and skinny and bought this to wear at home. It has a good fit overall and is comfortable. However, I noticed the torso is quite long and the crotch is a bit low. Still, I only use it at home, so not a big deal for me."

"I've never worn a union suit before, but I was pleasantly surprised. The quality of Carhartt is evident, and the multi-stitching really holds up well. The cuffs are longer than usual, making it easy to wear other clothing on top without bunching. The button-up system is well thought out, allowing easy access. Overall, I find them comfortable and warm for working outside in the cold."

"I work outdoors in Chicago and tested this suit in temperatures below 30°F. It's comfortable, but I found it only suitable as a single layer in those conditions. The cotton material is soft, and the buttons make bathroom breaks easy. However, it's not ideal for temperatures below 30°F without additional layers. It's a good quality suit for around 30-50°F weather."

"I've owned several union suits, and I keep coming back to Carhartt. They cut wind effectively and provide decent insulation for outdoor work in extreme cold. I've tried other brands, but Carhartt offers the best value for the quality. They're worth every penny for anyone who spends time outside in freezing conditions!"

"I was told it fits comfortably and looks nice. I'm considering buying one for myself this fall, preferably in colors like red, black, purple, or yellow, not white."

"I ordered these before and have always been pleased. However, this time the fabric was yellowed for the body and bright white for the arms and collar."

"I ended up purchasing three pairs! They fit just right, wash well, and don't shrink. At 5'4" and 130 lbs, I bought a men's large and it fit perfectly."

“I needed a product like a one-piece long john, so I opted for Made in Canada. The quality is excellent, and the material feels thicker. I got an XL size, which is a bit loose for me, but it fits well in the torso. I'm 6'1" and 225 lbs with a 38-inch waist, and these will suit taller and wider folks too. Plus, there's a clever feature at the bottom of each leg to stop them from creeping up the calf. I might get a Large for a snugger fit under my dungarees. I'm really pleased with this purchase.”

“I bought these for a friend, and they are loving them! They said it’s incredibly comfortable and warm. Definitely a win!”

“I've tried various long johns, usually needing an XL, but these were way too long for me! I have a short torso and long legs, so the fit was baggy, which I wasn't thrilled about. I do appreciate the soft fabric and warmth, though. I might try ordering a Large or even a Medium next time.”

"I ordered extra Union suits in various colors like charcoal and red. The green color reminded me of military wool blankets, though it’s more of a drab olive green than forest green. Regardless, they keep me warm during the chilly winter days as I wear them under my Santa Grinch suit while handing out gifts. I love layering and these long johns make popping outside enjoyable. My only concern is the snap feature; it’s tough to unsnap without risking a tear. Overall, I’m super happy with my purchase!"

"I absolutely LOVE these pajamas! I was on the hunt for a red onesie to match my baby for Christmas, and these are just perfect. They feel super soft and lightweight. I was worried about the buttons on the back, but they turned out to be quite comfortable. I prefer my pajamas to be loose, so I opted for an XL, and it gives that oversized feel. Plus, the button-down front makes breastfeeding a breeze!"

"This fits great and feels super soft while being surprisingly warm. For the price, it's hard to beat. However, if you’re like me—a decadent chocolate man—this might not be the best fit, as it can be revealing if you need to disrobe. The fabric is thin, but it’s breathable, so I might just wear it under my work clothes on those frigid days. Overall, I’d definitely buy it again!"

"I love this onesie, but it could really use a button in the back."

"I bought this for my husband, and it fit him great! He can tuck in the top, and the waistband is tight enough to keep it closed. Just wish the price was lower."

"I wore this for a week, and it’s great for keeping warm. However, after the first wash, two buttons popped off, and the back flap leaves my back exposed. I think it needs better design."

“I’m giving 5 stars because there was nothing wrong with the quality. However, these didn’t fit my boyfriend well at 6'5". I ordered an XL, but it was too short. We tried 2XL, but it still didn’t provide enough room. They’re thin, so great for layering but not suitable for tall guys with long torsos.”

“I rate these a single star. Despite knowing my size, the 5XL I ordered was ridiculously small. The material feels rough on the skin, and I struggled to put them on without help. They barely reached my shoulders, leaving 10 inches of open skin. This winter is going to be tough without proper union suits.”

“I’m absolutely thrilled with these! My husband had a pair 50 years ago, and he adores them. I initially checked Duluth Trading Company, but they hadn’t heard of this style. I recommend going a size larger.”

"I bought these thermals for a cold day at work, and to my surprise, my husband enjoys lounging in them too. They have a waffle texture with a soft touch of polyester, making them incredibly comfortable to wear. Happy husband, great purchase!"

"At 5'9” and 145 pounds, I typically wear a 32x34 in Levi's and a medium shirt size. I ordered a medium set, and while the top fits perfectly, the pants are a bit roomy in the top area. I expected the pants to have an elastic waistband like underwear, which they don't show in their ad. Despite this, they were inexpensive and keep me warm, so I'm satisfied."

"I'm 6'3" tall with long arms and usually wear 2XL or 2XLT in regular clothing. I ordered the 2XL in this thermal set. The bottoms fit well, but the top is a bit snug. If I order again, I’ll go for 3XL to get a better fit."

"I bought this Amazon Essentials Thermal Underwear Set for my boyfriend, as Kentucky winters can be freezing, and it was a great purchase! The material is soft and comfortable, and it keeps him warm without feeling bulky. The fit is true to size and allows for easy layering. He loves wearing it both outdoors and while lounging at home. It washes well too—no shrinking or pilling after several cycles. I highly recommend this cozy winter essential!"

"I ordered a size large, and they fit perfectly. I'm 6'2" and weigh 190 pounds. Working outside, I noticed a huge difference in warmth on the first day I wore them. With these thermals, I can remove a bulky outer jacket that restricts my movement. Highly satisfied with the purchase!"

"I got these as a surprise for my husband after being tired of his old ones with holes in the knees. He was ecstatic when he opened them! They're not scratchy, not heavy, and look stylish. They're also very breathable and flexible! The sizes are accurate, and overall, I give them five stars. My husband agrees!"

"I find the fabric incredibly soft and warm, making it worth the higher price. I ordered a size up, and it fits snugly. The zipper on the drop chute is fantastic, solving any side draft issues I've experienced with other thermals. I'm very pleased."

"I really loved how the fabric felt, but sadly, I had to pass it on to a friend. Even though I ordered an XXL, it just didn't fit my portly frame well enough."

"At 6' and 240 pounds, the XL was way too small for me, which was quite disappointing. I also waited a long time for delivery."