Horse obesity is a growing concern that can result in negative welfare. The role horse owners play in horse weight management is not well understood. This study aimed to: (1) explore the attitudes, beliefs, and perceptions of owners with overweight or obese horses regarding their horses’ weight; and (2) understand the motivators and barriers for owners to implement, improve and maintain weight management-related strategies. A semi-structured interview guide based on the Theoretical Domains Framework was developed. Qualitative interviews were conducted with 24 owners in Prince Edward Island, Canada whose horse(s) were previously classified as overweight or obese by a veterinarian. Interviews were analysed using template analysis, organising patterns in the data into a codebook and overarching themes. Owners believed horse weight management was important, however, their perceived complexity of the issue made the implementation of the weight management practices difficult. Owners held conflicting perceptions, viewing overweight horses as well cared for, yet recognised these horses were at increased risk for negative health outcomes. Ultimately, participants felt emotionally torn about compromising their horse’s mental well-being to address weight issues. Owners considered the practicality of weight-management strategies, the strategies’ effectiveness, and whether recommended strategies aligned with their beliefs regarding good horse care practices. Knowledge was embedded into owners’ understanding of horse weight, however, some highlighted that traditional knowledge dominates the equine industry hindering systemic industry change. Increased understanding of the effectiveness and impacts of weight management strategies on horses and fostering a society that recognises and accepts horses within a healthy weight range are warranted.