How long will it take to fix a behavioural issue? I've been training dogs for over 10 years and the most common question I get asked is how long will it take to train a dog. And there's no answer to that question. The learning depends on how committed the owner is to the training, severity of the issue, how long it's been going on etc. Fixing behavioural issues isn't easy due not only learning new behaviours but unlearning the old ones.