Objective: To compare chronic physical health disorder prevalence amongst Australian adults with and without mental illness. Method: Total n=1,716 particpants (58% female) with a mean age of 52 ± 13 years (range: 18 to 89 years) completed an online survey of Australian adults in 2010. Outcome measures including prevalence of chronic physical conditions and self-reported body mass index (BMI) in n=387 (23%) with a self-reported mental illness diagnosis were compared to respondents without mental illness. Results: A significantly higher proportion of participants with mental illness were obese (BMI ≥ 30; 31 vs 24%, p=0.005). Adjusted odds ratios (OR) for coronary heart disease, diabetes, chronic bronchitis or emphysema, asthma, irritable bowel syndrome, and food allergies or intolerances (OR range: 1.54-3.19) demonstrated that chronic physical disorders were significantly more common in participants with a mental illness. Conclusion: Australian adults with a diagnosis for mental illness have a significantly increased likelihood of demonstrating chronic physical health disorders compared to persons without mental illness. Implications: Health professionals must be alert to the increased likelihood of comorbid chronic physical disorders in persons with a mental illness and should consider the adoption of holistic approaches when treating those with either a mental or physical illness.