Your dog used to take the stairs at speed. This week they stand at the bottom, ears back, weight shifted away, and will not put a paw on the first step.
Two different things look identical from the hallway. One is a body that hurts. The other is a normal adolescent wariness that has landed on the staircase.
Rule out pain first
Pain frequently presents as a change in behaviour rather than as obvious lameness, and avoiding stairs is a common version of that. Adolescent dogs are also still growing, which is its own reason to check.
It appeared over days rather than weeks, or straight after one slip or fall.
Your dog is also slower to get up after resting, or favours one side.
They will go up but not down, which loads the front end differently.
They hesitate at the top or bottom, yelp, or look back at their own hips.
They are a large or giant breed between roughly 6 and 18 months old.
Safety note
Book a veterinary examination before you train anything if any of the points above apply. Sudden behaviour change warrants an examination, and pain frequently presents as a change in behaviour rather than as obvious lameness. Get help now if your dog cries out, goes stiff, will not weight-bear on a leg, or growls when touched near the hips or shoulders. That is a veterinary question, not a training one.
If your veterinarian finds nothing physical
New wariness of ordinary things is common in the second half of the first year. Owners and trainers commonly describe it as a second fear period, and it usually eases over weeks.
A staircase is a strong candidate for it. It is loud underfoot, it can be slippery, it drops away, and there is nowhere to stop and think halfway down.
One bad slip is often enough on its own. Your dog is not remembering the fall so much as the surface it happened on.
Do not carry your dog past it
Lifting your dog up and down teaches them that the stairs are something to be rescued from. Forcing, dragging or pushing teaches something worse.
Punishment-based approaches are associated with fear and avoidance, and here the fear is the whole problem. Reward-based methods are what the veterinary behaviour guidance recommends for this work.
This week: make the surface trustworthy
Add a non-slip runner, stair treads or a yoga mat over the first few steps. A dog who has slipped once is avoiding the surface, not the height.
Light the top and the bottom. Some dogs are stopping at a shadow rather than at a step.
Move your dog's bed, water and toys to the floor they spend the day on. The staircase should stop being something they face 8 times a day.
Put a gate at the bottom for 2 weeks if your dog keeps approaching and retreating. Every failed attempt rehearses the fear.
Then 3 minutes a day, bottom step only
Working below the point at which your dog reacts is the condition for learning near something they find frightening. On a staircase, that usually means one step, not a flight.
Sit on the third step with 15 treats. Feed your dog for standing on the floor near the bottom, doing nothing else, for 2 days.
Then toss 1 treat onto the bottom step. Let your dog choose to put a paw there. Feed again for that single paw, then stop for the day.
Add 1 step every 2 days, and only once the previous one is easy and unhurried. Going slower than feels necessary is what makes this hold.
Practise coming down as its own exercise, from the bottom step upward. Down is harder than up for most dogs.
If your dog stops taking food, you have gone too far. Go back 2 steps and finish there rather than on the hard rep.
Relaxation and confidence are trained as behaviours in their own right, in short repeatable sets below your dog's threshold. Three minutes is a session. Ten minutes of coaxing is not.
What to expect
Owners usually describe weeks rather than months, with progress that moves around from day to day. If your dog also refuses to jump into the car or onto furniture, treat that as part of the same veterinary question.
Comforting a frightened dog is not a mistake. If your dog comes to you at the bottom of the stairs, they are welcome. You cannot make fear worse by being kind to a scared dog.
Today's version, in one line: a non-slip mat on the bottom step, and 5 treats fed on the floor beside it.