Junior Trunk

Love them or they're free
$19 $17.10

Low as $15.20

Built for Kids
Anti-Chafe
Soft Bamboo Viscose
Anti-Sweat
Junior Trunk - Butter Nuts - Bamboo Underwear
Junior Trunk - Butter Nuts - Bamboo Underwear
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Junior Trunk

Love them or they're free
$19 $17.10

Low as $15.20

Built for Kids
Anti-Chafe
Soft Bamboo Viscose
Anti-Sweat
Junior Trunk - Black Currants Junior Trunk - Smashed Avo Junior Trunk - Ahoy Sailor Junior Trunk - Butter Nuts Junior Trunk - Scorpions Junior Trunk - Stormz Junior Trunk - Juicy Plums Junior Trunk - Snow Worries Junior Trunk - Starlight Junior Trunk - Snowballs Junior Trunk - NBL Melbourne United Junior Trunk - NBL Brisbane Bullets Junior Trunk - NBL Adelaide 36ers Junior Trunk - NBL Tasmania JackJumpers Junior Trunk - NBL Sydney Kings Junior Trunk - NBL SEM Phoenix Junior Trunk - NBL Perth Wildcats Junior Trunk - NBL Illawarra Hawks Junior Trunk - NBL Cairns Taipans

1. Select your size

2. Select your quantity

3. Select your colours

Black Currants
Smashed Avo
Ahoy Sailor
Butter Nuts
Scorpions
Stormz
Juicy Plums
Snow Worries
Starlight
Snowballs
NBL Melbourne United
NBL Brisbane Bullets
NBL Adelaide 36ers
NBL Tasmania JackJumpers
NBL Sydney Kings
NBL SEM Phoenix
NBL Perth Wildcats
NBL Illawarra Hawks
NBL Cairns Taipans
7
Free Shipping
30-Day Guarantee
Over 65k 5-Star Reviews

The ultimate underwear for boys aged 2-14, our trunks are made with all the same high-quality features as our adult collections. They are available in a range of fun colours and prints and feature our classic fabric which wicks away sweat and lets you breathe.

Our Junior Trunk range is made from 95% viscose made from bamboo and 5% spandex. This equals an extremely soft and durable pair of underwear that wicks sweat brilliantly.

The sizing is considered "fitted", meaning that if you are in between sizes, we would recommend sizing up.

We aim to dispatch your order 1-2 business days after placing your order.

Free shipping, no minimum spend.

GENERAL SHIPPING TIMES:

NSW, VIC & QLD = approx. 1-3 business days after dispatch.

WA, NT, TAS = approx. 2-4 business days after dispatch.

We offer international shipping to selected countries, which is shown at checkout. International shipping may vary based on local fulfilment.

We are so confident your kids will love their Step Ones, we'll give you a FULL REFUND on your FIRST PAIR if they don't like them for whatever reason.

We Science'd Underwear

We didn't just make underwear. We reinvented it. Now in kids sizes.

Ultra Soft Bamboo

Made from viscose made from bamboo — super soft and comfortable, with no itchy tags or scratchy seams. Happy kids mean happy parents!

Safe For Sensitive Skin

Our bamboo material is naturally hypoallergenic and antibacterial, meaning all kids have to worry about is where they are going to play next!

Built For Play

Reinforced stitching and high-quality bamboo fabric made for kids who can't sit still — they withstand endless adventures (and repeated washes).

Greg Taylor - CEO & Founder
Greg Taylor - CEO & Founder
26M+
Pairs Sold
65K+
5-Star Reviews
2M+
Happy Customers
Trustpilot

Trust Score 4.5/5

Real Results from Real Customers

Which Step Ones are right for me?

Compare our styles to find your perfect fit.

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  • 3D comfort pouch
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Trunk

Trunk

  • 4 inch in-seam
  • Anti-chafe Ultraglyde panels
  • Bamboo viscose fabric
  • Suits thinner legs
  • Good for shorter guys
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Boxer Brief Fly

Boxer Brief Fly

  • 6 inch in-seam
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  • Bamboo viscose fabric
  • Easy access front fly
  • 3D comfort pouch
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Boxer Brief Sport

Boxer Brief Sport

  • 8 inch in-seam
  • Anti-chafe Ultraglyde panels
  • Bamboo viscose fabric
  • Longer for activity
  • 3D Comfort Pouch
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30 Days

First Pair Guarantee

Love them or they're free. If your kids don't love their first pair, we'll give you a full refund.

Risk-free trial
Full refund

Frequently Asked Questions

Our kids range is made from high-quality, organically grown Bamboo Viscose with a touch of spandex. It's incredibly soft, breathable, and moisture-wicking — no itchy tags or scratchy seams.
Yes! Bamboo viscose is naturally hypoallergenic and antibacterial, making it gentle on even the most sensitive skin.
The Girls Shortie comes in Ages 6-7 through to Ages 12-14, and the Junior Trunk covers Ages 2-3 through to Ages 12-14. Use the Find my Fit guide on this page to match your child's measurements to the right size.
We are so confident your kids will love their first pair of Step One underwear that if they don't, you can keep them and we'll give you a full refund. No questions asked. This applies to your first single pair purchase.
Machine wash cold with like colors. Tumble dry low or line dry in the shade. Do not bleach, iron, or dry clean to maintain the quality of the bamboo fabric.