Accredited Exercise Physiologists are allied health professionals trained in the delivery of exercise and lifestyle interventions for people with chronic illness including mental illness. This study aimed to investigate how Accredited Exercise Physiologists engage in the treatment of people with a mental illness. Accredited Exercise Physiologists were invited to complete an online survey via communication from Exercise and Sports Science Australia. Sixty-one Accredited Exercise Physiologists completed the online survey. The majority of AEPs agree that exercise is valuable in the treatment of people with a mental illness. General Practitioners are the most common referral source. Exercise Physiologists believe more people with a mental illness should be referred for services, however more than half agree that people with a mental illness are likely to be less adherent to an exercise intervention compared to people without a mental illness. More than half of respondents report no formal training in training in the prescription of exercise for people with a mental illness however 89% believe additional professional development would be beneficial. Given the support for the efficacy of exercise in the treatment of people with mental illness, this group of health professionals appears to be an underutilised resource.