From early on in the domestication history of horses, their relationship to humans has been largely centred on a working relationship through harnessing and riding. Archaeological studies trying to evaluate when horse riding first occurred are largely based on examination of the animal’s teeth and spine, both showing traces of bit actions and rider’s weight on the back respectively. Thus, work does affect the horse’s body but the question remains of whether this is so that horses’ welfare may be altered both during the working sessions and/or in a more chronic way with consequences outside work. Here we will review the existing evidence of the potential effect of work on the overall welfare state of horses and try and identify the behavioural indicators of discomfort at work as well as the indicators of work related problems outside the working situation. We will end with positive practices that may favour the horse’s good perception of working time and thus enhance human security.