A puppy can outgrow a harness before they’ve worked out what a walk is.
We make ours adjustable so there’s room for the next growth spurt. The trick is getting a good fit today, with more strap to let out tomorrow.
A small puppy harness is a fiddly thing to make.
The puppy gets smaller. The buckles, sliders and rings still need somewhere to go.
That leaves very little room to get the straps sitting properly. We make our smaller harnesses with the same care as the big ones, checking the proportions and where the fittings land. A tiny chest deserves a proper fit too.
20 mm straps. Room to grow.
Our smaller MTF harnesses use 20 mm webbing. The adjusters let you lengthen the straps as your puppy’s measurements change, so a growth spurt needn’t mean starting again.
The aim is simple: keep a well-fitting harness in use for longer. Less replacing. More getting out together.
Fits today.
Choose for the puppy in front of you. The harness should sit securely at their current measurements.
Adjusts for tomorrow.
Let the straps out as they grow, while every part still sits where it should.
20 mm is the strap width, not the size. The adjustment range is what gives them growing room. Some puppies will eventually need a larger harness. We’ll help you check the fit rather than guess how many months it will last.
How to choose the right puppy harness size
- Measure your puppy now, in cm. Use the measurements shown in the harness size guide, rather than their age or expected adult size.
- Check both ends of the size range. It needs to fit now, with adjustment left to let out. Don’t buy an oversized harness for them to grow into.
- Check the whole fit. The neck, chest and connecting straps all affect where it sits. A chest measurement is only the start.
Use our harness measuring guide. If the adjustable sizes don’t suit their proportions, made-to-measure is available.
Most puppies start in our XS. It’s made with the same 20 mm webbing as our other smaller harnesses and collars, so it’s light enough for a small puppy and adjusts as they grow. Between sizes, growing fast or an unusual shape? Choose CUSTOM and we’ll make it to their measurements.
Very small puppy? Ask us first.
Send their current measurements. We’ll check how the 20 mm straps and fittings will sit on their frame before you order.
A first puppy collar, too.
A puppy collar carries their ID tag and gets them used to wearing something light. Measure their neck in cm, choose the size where today's measurement sits comfortably in the range, and check you can slide two fingers underneath. Our collars adjust, so a growing puppy collar can be let out as they fill out.
For walks and lead practice, clip the lead to the harness rather than the collar. It keeps pressure off their neck while they learn.
Little shoulders. Room to move.
A well-fitted Y-shaped front leaves the shoulders clear and sits away from the throat. Check that the chest strap sits behind the front legs without rubbing the armpits.
Watch your puppy move, then recheck the fit. Straps should stay in place without digging in or leaving a loose gap they could slip through. Follow the harness’s fitting guide, and check for wear or chewing too.
First harness. Small steps.
Let them sniff it first. Reward calm interest, then build up to wearing it in short, gentle sessions at home. If they back away, pause and make the next step easier.
Give them time to get comfortable before the first outing. Dogs Trust’s harness introduction guide shows the process.
A puppy harness and lead set, ready for practice.
We recommend our hands-free dog lead for walks and training. Reclip it into a hand-held lead for those first loose-lead lessons, with the hands-free option there when you want it.
One lead for practising together and heading out together. Choose a length and fittings that suit your puppy, and match the print to their harness if you fancy. Choose the collar, harness and lead in the same print for a matching puppy collar and lead set.
Already fully grown, just small? Our small dog harness guide covers straps, buckles and adult proportions.
Before their first walk.
Can one harness grow with my puppy?
Adjustment can keep a harness in use as they grow, within its size range. It can’t make every puppy harness fit an adult dog. Keep checking the fit, and move up when the straps or proportions no longer suit them.
How often should I check the fit?
Check before each walk, especially while they’re growing quickly. Remeasure if you’re letting straps out, noticing rubbing or seeing the harness shift as they move.
Can I get a matching puppy harness and lead?
Yes. Our prints run across harnesses and leads. We recommend the hands-free dog lead for its different wearing options and hand-held setup for training. Check the lead and fittings suit your puppy’s current size.
What size collar does a puppy need?
Measure their neck now and choose the size where that measurement sits within the range, with room to let it out. Check the fit every week or two while they grow.
Should I walk my puppy on a collar or a harness?
Use the collar for their ID tag and a well-fitted harness for walks and lead training.
Small dog. Big plans.
Made in Bristol, UK. Adjustable sizes to start with, and made-to-measure if their proportions need it.
Explore our dog harnesses →Ask us about puppy fit →Start with the Holy Cow Y-shaped dog harness. Add the matching hands-free dog lead when its clips and width suit your puppy.
Sources and further reading
By Mind The Fluff. Product details refer to our own harnesses. General fitting and introduction guidance checked 20 October 2026.