Maximal aerobic capacity (VO2max) is a good indicator of overall health and is commonly measured in the general population, but often goes overlooked in individuals with SMI. Previous studies involving exercise and SMI focus mainly on self-perception and mood. Only one study has measured the VO2max in this select population while promoting exercise and dietary changes. Purpose: To assess the maximum aerobic capacity, weight, and body fat percentage (BF%) in individuals with SMI. Methods: Weight, BF%, and VO2max were measured prior to wellness intervention (pre) and following wellness intervention (post). Forty-nine individuals (27=male, 22=female) with a mean age of 43±13.20 years of age and a diagnosis meeting the criteria for severe and persistent mental illness (SMI) were assessed. SMI classification among the subjects as follows: schizophrenia (n=11), bipolar disorder (n=17), schizoaffective disorder (n=14), major depressive disorder (n=7). Results: No significant difference was observed between baseline and endpoint measurements of BF% in all diagnoses except MDD. Males with MDD benefited from a wellness intervention with a significantly lower BF% (p(.036);p<0.05). A wellness intervention did not increase in the VO2max in individuals with SMI (p(.0358);p<0.05). Individuals with SMI continually rated in the very poor to poor section for VO2max. Conclusion: Individuals with SMI tend to have low aerobic capacity and high body fat percentage. Individuals in the current study did not benefit from a wellness intervention in terms of BF% and VO2max except males with MDD. Males with MDD significantly lowered their BF% following a wellness intervention.