Purpose: Although burnout is associated with erosion of professionalism and serious personal consequences, whether positive mental health can enhance professionalism and how it shapes personal experience remain poorly understood. The study simultaneously explores the relationship between positive mental health and burnout with professionalism and personal experience. Method: The authors surveyed 4,400 medical students at seven U.S. medical schools in 2009 to assess mental health (categorized as languishing, moderate, and flourishing) and burnout. Additional items explored professional behaviors, beliefs, suicidal ideation, and serious thoughts of dropping out. Results: A total of 2,682/4,400 (61%) responded. Prevalence of suicidal ideation (55/114 [48.2%], 281/1,128 [24.9%], and 127/1,409 [9.1%]) and serious thoughts of dropping out (15/114 [13.2%], 30/1,128 [2.7%], and 14/1,409 [1.0%]) decreased as mental health improved from languishing, moderate, and flourishing, respectively (all P < .0001); this relationship between personal experience and mental health persisted independent of burnout (all P < .001). As mental health improved, the prevalence of unprofessional behaviors (i.e., cheating and dishonest behaviors) also declined, whereas students' altruistic beliefs regarding physicians' responsibility toward society improved. For example, 33/113 (29.2%), 426/1,120 (38.0%), and 718/1,391 (51.6%) of students with languishing, moderate, and flourishing mental health endorsed all five altruistic professional beliefs (P < .0001). The relationship between professional beliefs and mental health persisted among students with burnout, whereas fewer relationships were found among students without burnout. Conclusions: Findings suggest that positive mental health attenuates some adverse consequences of burnout. Medical student wellness programs should aspire to prevent burnout and promote mental health.