Non-suicidal self-injury (NSSI), the intentional damage to body tissue without the intent to die, is a prevalent public health problem in the U.S. and around the world. The current study sought to identify intrapersonal (emotional reactivity) and interpersonal (emotional expressiveness to others) correlates of NSSI in order to provide insight into how to best tailor prevention and treatment efforts. Four hundred and forty nine college students were surveyed about various psychological characteristics as well as engagement in NSSI. Results indicated that those who have difficulty expressing emotions are at an increased risk for NSSI even after controlling for depressive symptoms and that emotional expressiveness acts as a partial mediator between depression and NSSI. Emotional expressiveness should be a target of treatment among people who engage in NSSI.