This pilot study examined whether participation in the individualized, community-integrated In SHAPE health promotion program would result in improved physical activity and dietary behaviors, health indicators, and psychological functioning or symptoms in 76 adults with schizophrenia, bipolar disorder, major depression, or other mental disorders. Over a 9-month period, participation was associated with increased exercise, vigorous activity, and leisurely walking (P < .01), and a trend toward improved readiness to reduce caloric intake (P = .053). Participants demonstrated a reduction in waist circumference (P < .05), but no change in BMI. Satisfaction with fitness (P < .001) and mental health functioning (P < .05) improved, and severity of negative symptoms decreased (P < .01). This study demonstrated the feasibility and potential effectiveness of the In SHAPE program, which consisted of exercise and dietary modification. Based on these promising results, randomized controlled trials of the In SHAPE program are necessary to establish its effectiveness compared with usual care and alternative approaches to enhancing fitness.