Background Equine obesity is a significant health and welfare concern. The proportion of domestic horse populations that are overweight are as high as 45%. As the primary decision-makers for their horses’ care, owners are theoretically ideally placed to identify whether their horses are appropriately conditioned, however, research in other countries has shown that many owners are unable to accurately judge their horse’s body condition. In this study, through the comparison of body condition scoring (BCS) performed by an expert and the horse owners and interviews with owners, we aimed to identify the proportion of horses that were overweight or obese, to assess the accuracy of horse owners' BCS assessment both prior to and after receiving information and instructions on body condition scoring, and to identify common themes amongst owners’ views regarding BCS assessment and the Henneke BCS system. Results Forty-five percent of the horses in this study were overweight or obese. The agreement between the owners and an equine veterinarian regarding the horses’ BCS was fair to good both prior to (κ = .311, P < 0.001; ICC = .502, P < 0.001) and after (κ = .381, P < 0.001; ICC = .561, P < 0.001) receiving information and instructions on scoring. Three quarters of the owners who took part in the study did not use any method of monitoring their horse’s body condition. Thematic analysis of owner responses was varied, with the most common theme being an awareness of the need to monitor or make changes to their horse’s condition with responses in this theme split between owners who felt in control and those who did not. Owner feedback on the utility and useability of the scorning system was that it was useful however parts are too technical or need improvement. Conclusions Equine obesity is a significant problem in this population in Ireland. Horse owners’ ability to accurately judge their horse’s condition does not improve with provision of instructions on body condition scoring. These results combined with owners’ feedback on the Henneke BCS system indicate that it is not a tool that can be reliably used by owners.