Self-injury as defined in this study is the deliberate infliction of harm to ones’ body (often cutting or burning) without suicidal intent. The increase in self-injurious behaviour in North American society is puzzling to understand and difficult to treat. In several explanatory models, self-injury is conceptualized as a method for coping with overwhelming negative emotions. The Experiential Avoidance Model (EAM; Chapman, Gratz, & Brown, 2006) has been hypothesized to be a unifying theoretical framework offering a basis for future research. The EAM proposes that self-injury is a method used to avoid uncomfortable and unmanageable affect, which is then reinforced by escape conditioning and negative reinforcement. This study tested the EAM as well as the underlying vulnerabilities that contribute to experiential avoidance in a sample of 132 self-injurers recruited from the general population. A vulnerability that was hypothesized to contribute to experiential avoidance was insecure attachment through its impact on the other EAM components such as affect intensity, emotion valence, and affect regulation abilities. A control group consisting of 117 participants that did not have a history of self-injury or current mental health concerns were used in this study as a point of comparison on all measures. The results highlight that self-injury serves multiple functions, although emotion regulation is its predominant function. The data provided an acceptable fit to path models that tested the EAM as well as an expanded model of EAM that included anxious/ambivalent attachment. The results highlight complex models that include multiple direct and indirect relations between the variables involved in the frequency of self-injury. Experiential avoidance had a direct effect on the frequency of self-injury. Other results indicate that avoidant attachment plays a role in self-injury as do aversive emotions, specifically guilt. Treatment of self-injury needs to address several areas of deficits, particularly those related to emotion dysregulation. The implications of the findings are discussed in relation to the existing literature, treatment, and areas for future research.