The thoroughbred horse breeding industry contributes significantly to the Irish economy. However, staff shortages threaten the economic sustainability of the industry, as well as the welfare of both horses and workers. Previous research on the staffing crisis faced by the broader horseracing industry has highlighted mental health concerns as a factor. Furthermore, the influence of workplace context on mental health has been widely recognised in organisational psychology. The aim of this study was to assess prevalence rates of Common Mental Disorders (CMDs) in Irish thoroughbred horse breeding and associated occupational risk factors. Thoroughbred breeders and stud farm staff (N = 105) were recruited through key industry organisations for a survey consisting of four sections including demographic and lifestyle, mental health, occupational risk factors, and wellbeing at work. CMD prevalence encompassed depression, anxiety, psychological distress and substance use. Occupational risk factors including career dissatisfaction, job control and workplace bullying were assessed to explore associations. Descriptive statistics estimated prevalence, while inferential analyses explored associations between demographic and occupational factors. Breeding staff reported high rates of depression (50%), psychological distress (44.3%), anxiety (34.9%), and hazardous alcohol consumption (45.3%). Low job control, bullying, injuries, and career dissatisfaction were each associated with increased CMD prevalence. Women and younger staff were at an increased risk of bullying, CMDs, and lower wellbeing. This is the first study to assess CMD prevalence and risk factors in thoroughbred breeding in Ireland. High prevalence rates of CMDs and staff leaving intentions are influenced by occupational factors in thoroughbred breeding.