Military Veterans have a higher risk of incident atherosclerotic cardiovascular disease (ASCVD) than the general population and are often clinically complex. We studied the changes in cardiovascular risk factors with a lifestyle intervention in this population. We retrospectively analyzed data from 67 participants (mean age 69.2 (SD 7.9) years; 97% male) with atherosclerotic heart disease and/or type 2 diabetes in a 15-week, multiple health behavior change (MHBC) intervention implemented in a Veterans Affairs (VA) Behavioral Medicine Clinic. The intervention promoted a whole foods, plant-based (WFPB) diet, physical activity, and cognitive-behavioral stress management. We assessed cardiometabolic risk factors at baseline, 1 month into the intervention, and at 15 weeks (post-treatment). Among intervention completers (n = 67), we observed statistically significant improvements in waist circumference (-2.8 inches, = .03), systolic blood pressure (-7.9 mmHg, = .03), LDL cholesterol (-11.27 mg/dL, = .04), fasting glucose (-15.10 mg/dL, = .03), and hemoglobin A1c (-0.55%, = .017) at post-treatment. Participants with type 2 diabetes (n = 34) achieved improvements in hemoglobin A1c (-0.80%, = .007), systolic blood pressure (-10.98 mmHg, = .01), and diastolic blood pressure (-6.65 mmHg, = .03) at post-treatment. Medication usage did not significantly change. Veterans who completed the MHBC intervention achieved significant improvements in cardiometabolic risk in a routine VA clinical practice setting.