Beliefs about how much people can change their attributes—implicit theories—influence affective and cognitive responses to performance and subsequent motivation. Those who believe their attributes are fixed view setbacks as threatening and avoid challenging situations. In contrast, those who believe these attributes are malleable embrace challenges as opportunities to grow. Although implicit theories would seem to have important mental health implications, the research linking them with clinical applications is limited. To address this gap, we assessed how implicit theories of anxiety, emotion, intelligence, and personality related to various symptoms of anxiety and depression, emotion-regulation strategies, and hypothetical treatment choices (e.g., medication versus therapy) in two undergraduate samples. Across both samples, individuals who believed their attributes could change reported fewer mental health symptoms, greater use of cognitive reappraisal, and were more likely to choose individual therapy over medication. These findings suggest that implicit theories may play an important role in the nature and treatment of mental health problems.