A set of thermals is a practical and comfortable way to help kids keep warm as the temperature drops. With fitted cuts and moisture-wicking properties, the very best kids’ thermals are soft and breathable and work as an extra layer under normal clothes.
While many thermals are multi-purpose and work just as well as insulated layers for outdoor play as they do for keeping toasty on lazy mornings at home, others have to work a bit harder. In our tried and tested review, we’ve included day-to-day thermals as well as extra-warm base layers suitable for winter sports and sub-zero temperatures.
Material is a big consideration. Some are a cotton mix, while others use temperature-regulating materials like bamboo. Merino wool is a very popular choice for base layers – it’s a breathable fabric so ideal for temperature regulation and is great at wicking moisture away from the body to keep little ones dry, even after a full-on snowboarding session. It’s also antibacterial, and anti-odour, so it doesn’t need washing as often as other materials – always a bonus.
As thermals or base layers are going to sit next to the skin, you want something soft and not itchy if you have any chance of convincing a child to wear them. While merino is finer than typical sheep’s wool, as well as being non-allergenic, some children find it a little itchy on the skin. The ones we’ve reviewed all got the thumbs up from our little testers for softness and zero itch.
Versatility is important when investing in some decent kids’ thermals, and the ones featured here are all excellent multi-taskers, working as thin base layers, cute pyjamas or stylish comfies for chilling out at home or heading out on playdates.
How we tested
Our group of mini testers, ranging from four to nine, really put these thermals and base layers to the test. Worn for extra warmth on school cross country races and on a walking holiday, to heavy-duty base layers on a freezing trip to Lapland – oh, and lazing around at home – our child testers put these thermals through their paces. We looked at comfort, warmth, fit, quality and ease of washing, along with value for money. Here are the ones that really impressed us.
Why you can trust us
Sarah Dawson is a seasoned tester of children’s clothing. With the help of her kids (ranging from four to nine), she’s hand-tested a wide range of cold-weather gear, including raincoats, always making sure to be inclusive of all budgets. She takes testing seriously and has taken her kids on adventures, such as Lapland and the Lake District to really put these thermals through their paces. When reviewing kids thermals, she’s taken into consideration a huge range of factors, including how the fabric feels on the skin as well as how they wash.
The best kids thermals for 2024:
Roarsome bamboo base layer set
Ticking all our boxes for warmth, style and softness, this great value set from Roarsome is the ultimate multi-tasker. They were a clear favourite with our testers who loved the simple cut and silky-soft material – and they performed perfectly as breathable base layers when out hiking, as well as running in a very cold cross-country race. There was no overheating or clamminess, just the right amount of insulation. Stylish and comfy enough to double as pyjamas and general loungewear at home, they have been worn on repeat since we began testing.
Made from sustainable, premium bamboo – great for naturally regulating the body temperature as well as being hypoallergenic – we found these to be such a brilliant choice for children who declare most fabrics “itchy”. They are also really easy to machine wash and tumble dry, with no need for special detergents or machine settings. These base layers are buttery soft and come in an assortment of colours, with sizes ranging from age one to 10. We think the Roarsome base layers offer serious value for money and are worth every penny.
Buy now £35.00, Roarsome.com
Damart thermal medium warmth long pants and long sleeve top
Simple yet effective, these thermals from Damart are great for keeping younger kids cosy. You can pick the level of warmth needed – we tested out level three, which is medium warmth, designed for winter wear. Our younger tester was kept nice and toasty at home and when out and about. The material itself is very soft and lightweight enough to layer under clothes for forest school or outdoor nursery, with sizes ranging from two years up to 14.
The set is a breeze to machine wash and tumble dry, without any shrinkage or bobbling. Both the top (£15, Damart.co.uk) and leggings (£15, Damart.co.uk) make a handy addition to any child’s winter wardrobe.
Buy now £15.00, Damart.co.uk
Icebreaker kids’ merino 200 oasis thermal top and leggings
Made from 100 per cent merino wool, these stylish base layers got the no-itch seal of approval from our testers, who loved the soft feel. With flatlock seams and no annoying label at the neck, they scored high for comfort and the lightweight material makes these a perfect choice for low-bulk, winter sports base layers. However, the cool styling details, like the logo-print elasticated waist and blaze orange colourway, made these a massive hit for simple everyday wear as well.
The moisture-wicking and breathability were put to the test climbing fells in the Lake District and were suitably impressed. Everything about the top (£45, Icebreaker.com) and leggings (£45, Icebreaker.com) feel premium and, even after machine washing (we used the wool cycle and wool detergent) and line drying, they have retained that exceptionally soft feel. Yes, they are an investment price-wise, but these thermals are designed to last and be passed down the family – the quality is undeniable.
Buy now £45.00, Icebreaker.com
Helly Hansen kids’ merino wool base layer set
We love the clever two-in-one design of these base layers which have a merino wool exterior (for insulation) and Helly Hanson’s unique super-soft fibres next to the skin, to wick away moisture and help regulate the wearer’s temperature. Our five-year-old tester loved the softness of this set and has declared them her favourite “comfies” – the fact they come in a hot pink camo design certainly helps too.
Fit details, such as the dipped hem at the back of the top, wide cuffs and fleecy reinforced knees, all upped the comfort factor. The cut is snug, yet stretchy, making it ideal for layering – although when base layers look this fancy it almost feels a waste to hide them away.
Buy now £65.00, Hellyhansen.com
Mountain Warehouse Merino kids II baselayer top and pants
If you’re after extra warm base layers on a budget, it’s hard to beat this top (£16.99, Mountainwarehouse.com) and pants (£16.99, Mountainwarehouse.com) set from Mountain Warehouse. Cosy, while still being lightweight and breathable, and with all the antibacterial and moisture-wicking features you’d expect.
We put these to the ultimate test on a family holiday to Lapland. Worn under another layer and snowsuit, these kept our four-year-old and seven-year-old testers at the perfect temperature – never too hot or too cold – even in -24C. They pass the no-itch test, no problem, and work really well as toasty pyjamas or comfy clothes to wear around the house. The raglan sleeves and contrasting cuffs and stitching definitely earn some style points too.
Buy now £16.99, Mountainwarehouse.com
Smalls Merino long sleeve top and 24 hour trouser
So much more than simple thermals, these super luxurious and soft merino layers from independent British brand Smalls Merino deliver next-level comfort and style. The foldable cuffs and drawstring waist of the trousers (£79, Smallsmerino.co.uk) help achieve the perfect fit, while the thoughtful addition of pockets made these an absolute favourite with our little testers. Our eight-year-old tester lives in his Smalls set now.
We also love the brand’s dedication to only using ethically made and fully traceable merino wool with sustainability and workers’ rights at its heart. While these thermals aren’t cheap, the quality is outstanding and the eco-friendly ethos makes the investment worthwhile.
Buy now £47.00, Smallsmerino.co.uk
Wheat wool Alfie T-Shirt and wool Agi leggings
These may be the thinnest thermals we tested, but they still provided plenty of warmth, keeping our little tester toasty at home and as base layers for outdoor adventures. Made from merino wool, the T-shirt (£34.95, Wheat.co.uk) and leggings (£29.95, Wheat.co.uk) set is lightweight and sit gently on the skin, with no itchiness reported by our five-year-old. Thanks to the featherlight feel, these are a great choice if your child doesn’t like bulky layers or is particularly active and hates to be restricted by clothing. We’ve washed on a wool setting in the machine, and they’ve come out looking as new.
What makes these stand out from the others in our round-up is the stylish choice of colours and patterns. We loved the Scandi-chic florals and stripes, which elevate these from basics to layers you want to show off.
Buy now £34.95, Wheat.co.uk
PO.P thermal merino kids top and leggings
These well-made separates from PO.P are a brilliant option if you’re looking for decent all-rounders. The merino fabric makes them thin, lightweight and flexible enough to wear as winter sports base layers or just as an additional layer of cosiness on cold days.
Breathable, antibacterial and anti-odour, our testers have worn these many times and we still haven’t needed to put them in the machine (on a wool cycle) thanks to the natural self-cleaning properties of the wool – we’ve found simply hanging them up to air has done the trick.
Foldable cuffs and plenty of stretch guarantee a good fit wherever your child sits in the age range. Available in six colours and in a simple classic cut, these are designed to be worn, enjoyed and passed down through the family.
Buy now £21.00, Polarnopyret.co.uk
Muddy Puddles thermal baselayer top and bottoms
Comfortable, durable and breathable, these fun base layers from Muddy Puddles are just the thing for keeping active kids cosy and unrestricted. The brushed inside feels very soft next to the skin, while still wicking any moisture away. A popular choice with our testers thanks to the soft feel, space print and thumb holes (designed to help kids get extra layers over the top without sleeves riding up) these have doubled as cosy base layers as well as warm PJs to beat the chill.
As parents, we were pleased that these versatile thermals can be machine-washed easily and are designed to withstand whatever your child can throw at them.
Buy now £17.60, Muddypuddles.com
M&S two-pack heatgen thermal vests
Long-sleeve thermals can be a little impractical for school, which is where these classic thermal vests from M&S really come into their own. Layering under polo shirts or PE tops, they are ideal for beating the chill as temperatures drop.
The soft brushed fabric got our tester’s seal of approval and washes well (we’ve seen no sign of bobbling). What’s more, there are no annoying labels around the neck. Just the thing for adding an extra layer of warmth without adding any bulk.
Buy now £10.00, Marksandspencer.com
The Verdict: Kids’ thermals
For comfort, softness, durability and value for money, our top pick has to be the Roarsome bamboo base layer set. An instant hit with our testers, they are a fantastic versatile addition to any child’s winter wardrobe. If you’re looking to invest in some hard-working base layers for a family skiing holiday, we can’t recommend the Icebreaker merino wool layers enough – excellent quality, made to last and worth the higher price tag.
To keep your home cosy and toasty all season long, check out our review of the best electric heaters
