My dog acts crazy around other dogs - but only on leash

The Causes of Leash Aggression

Is your dog acting crazy on-leash when he sees another dog?
Is he lunging, barking, growling, and jumping toward the other dog?

This set of behaviors is commonly referred to as leash aggression.

It’s a topic I get asked about all the time, and it’s something many dog owners struggle with.
It’s also a behavior that is often misunderstood.

And honestly, it makes sense! How confusing is it when your dog is totally fine with other dogs off-leash but then freaks out the moment the leash is on?

Like with most dog behaviors, finding the root cause is the key to creating a sustainable training plan that actually helps.

So, why does leash aggression happen?

Most cases of leash aggression stem from one (or a combination) of these factors:

• Fear
• Frustration
• Lack of proper socialization

But there’s another big reason:

Leashes are unnatural for dogs.

Here’s why that matters:

• The leash creates tension and prevents natural body language.
• If a dog feels threatened, his natural response is often to move away—but on a leash, that’s not an option. This can increase stress and reactivity.

And what happens then?

Over time, your dog may start associating the sight of other dogs (or other triggers) with frustration or anxiety, reinforcing the aggressive response.

Whether it’s fear, frustration, a lack of socialization, or something else, understanding the root cause of your dog’s leash aggression is the first step toward positive change.