The short answer: most dogs that bark at other dogs on walks are not being aggressive. They are either frustrated because they want to say hello and the lead will not let them, or they are scared and trying to make the other dog go away. Both look dramatic, but neither means your dog is dangerous.
Once you know which feeling is driving the barking, it becomes much easier to help.
Frustration barking
A frustrated dog usually pulls toward the other dog, whines or yelps between barks, and wags its tail. The body language says “I want to get over there” rather than “stay away.” This is the more common pattern, especially in younger dogs that have not learned to stay calm on a lead.
The lead itself is part of the problem. Off-lead, many of these dogs greet other dogs politely. On lead, they cannot move freely, and the tension builds until it comes out as noise.
Fear barking
A fearful dog looks different. The body is stiff or low, the tail is tucked or still, and the dog may lunge forward and then dart back. The bark is sharper and more rhythmic. The goal is distance — the dog wants the other dog to leave.
Fear-based barking often starts after a bad experience with another dog, but it can also develop in dogs that were not socialised enough as puppies. It tends to get worse over time if the dog keeps being put in situations that feel threatening.
Why it gets worse if you do nothing
Each time your dog barks at another dog and that dog walks away, your dog learns that barking works. The other dog was going to walk past anyway, but your dog does not know that. From their point of view, the noise solved the problem. This makes the barking more likely next time, not less.
Pulling the lead tight, shouting, or forcing your dog closer to the other dog all tend to increase stress, which makes the reaction stronger.
What helps
Distance first. When you see another dog coming, move far enough away that your dog notices but does not react. This distance is different for every dog — for some it is five metres, for others it is thirty. Start where your dog can stay calm.
Reward the calm. When your dog sees another dog and does not bark, mark that moment with a treat or quiet praise. You are teaching your dog that other dogs predict good things, not threat.
Turn and walk away. If your dog is already barking, do not wait it out. Turn smoothly and walk the other way. There is no learning happening once the dog is over its threshold — only stress. Try again from a greater distance next time.
Consistent routes at quiet times. Practise on routes and at times where you can control the distance. Busy parks at peak hours are not the place to work on this. Early mornings or quieter streets let you set the dog up to succeed.
Professional help. If the barking is intense, happens on every walk, or is getting worse, a qualified trainer or behaviourist is worth the investment. They can tell you whether the issue is frustration, fear, or something else, and build a plan around your specific dog.
When barking means something medical
Occasionally, a dog that was previously calm around other dogs starts reacting on walks. A sudden change in behaviour is worth a vet check. Pain, vision loss, or hearing changes can all make a dog more reactive because they feel less safe.
Matching the walk to the dog
A dog that is under-exercised or mentally bored is more likely to be reactive on a walk. Making sure the walk itself is the right length and pace for your dog’s breed and age helps bring the baseline stress level down. The walk-length calculator is a good starting point.
German Shepherd Dogs, for example, need significant daily exercise and mental engagement. An under-walked shepherd is more likely to redirect that pent-up energy into leash reactivity.
If your dog also pulls hard on the lead — which often goes hand in hand with barking at other dogs — see why your dog pulls on the leash for practical steps that work alongside the advice here.
For more on the behavioural research behind reactivity and socialisation in dogs, see our sources.