Abstract Context Physical inactivity promotes insulin resistance and increases the risk of diabetes and cardiovascular disease. Recently introduced clustering based on simple clinical measures identified diabetes subgroups (clusters) with different risks of diabetes-related comorbidities and complications. Objective This study aims to determine differences in physical fitness and cardiovascular risk between diabetes subgroups and a glucose-tolerant control group (CON). We hypothesized that the severe insulin-resistant diabetes (SIRD) subgroup would be associated with lower physical fitness and increased cardiovascular risk. Methods The physical fitness and cardiovascular risk of 746 participants with recent-onset diabetes (diabetes duration of < 12 months, aged 18-69 years) and 74 CONs of the German Diabetes Study (GDS), a prospective longitudinal cohort study, were analyzed. Main outcome measures included physical fitness (VO2max from spiroerogometry), endothelial function (flow- and nitroglycerin-mediated dilation), and cardiovascular risk scores (Framingham Risk Scores for Coronary Heart Disease [FRS-CHD] and Atherosclerotic CardioVascular Disease [ASCVD] risk score). Results VO2max was lower in SIRD than in CON, severe autoimmune diabetes (SAID) (both P < .001), and mild age-related diabetes (MARD) (P < .01) subgroups, but not different compared to severe insulin-deficient diabetes (SIDD) (P = .98) and moderate obesity-related diabetes (MOD) subgroups (P = .07) after adjustment for age, sex, and body mass index. Endothelial function was similar among all groups, whereas SAID had lower FRS-CHD and ASCVD than SIRD, MOD, and MARD (all P < .001). Conclusion Despite comparable endothelial function across all groups, SIRD showed the lowest physical fitness. Of note, SAID had the lowest cardiovascular risk within the first year after diabetes diagnosis compared to the other diabetes subgroups.