Nonsuicidal self-injury (NSSI) is an increasing health problem among college students. Research about risk factors behind the development of this behavior has been limited. This study aims to test whether emotion regulation mediates the connection between romantic relationships and NSSI. Participants were 566 college students (72.8% female) between 18 and 35 years old. Eighty participants (14.1%) reported having injured themselves. Emotion regulation fully mediated the associations between NSSI and four important subdomains of romantic relationships, namely, avoidance of intimacy, anxiety over abandonment, violence victimization, and violence perpetration. We specified a model that evidences the mediating role of the emotion regulation between romantic relationships (romantic attachment and intimate partner violence) and NSSI. This study makes a unique contribution by assessing the pathway through which romantic relationship functioning impact NSSI.