Individuals who report discussing their experiences of nonsuicidal self-injury (NSSI) may prefer to seek out nonprofessionals, rather than professionals or other stakeholders. The manner by which people respond to others’ self-injury experiences may influence future help-seeking and disclosure experiences as well as one’s NSSI trajectory. Unfortunately, some research suggests that how individuals respond to NSSI may not always be helpful. Moreover, only a paucity of research has formally examined what may contribute to helpful versus unhelpful responding to NSSI. Knowing what psychological processes are involved in these contexts may help to foster more effective responses to NSSI in general, NSSI disclosures, and NSSI help-seeking. Broadly, elucidating these processes also serves to conceptualize the stigma that is often associated with NSSI behaviours. Thus, the present dissertation applied a theoretical model, the Attribution- Affect-Action (AAA) Model of Helping, to NSSI. The model proposes that in the case of helping others with stigmatized conditions, attributions of controllability of cause for the condition negatively relate to helping intentions, a relation that is mediated by emotional reactions (e.g., anger, sympathy) towards the individual in need. Three separate studies were conducted, with participants recruited from Amazon’s Mechanical Turk, in an attempt to understand how people in the general public might respond to those who engage in NSSI. The role of gender was also explored. As a pilot, Study 1 informed the design for subsequent studies and also identified variability in what constitutes controllable and uncontrollable causes of self-injury. Building on this, Study 2 partially supported the usage of the AAA Model of Helping for NSSI; causal attributions of controllability were significantly and negatively linked to helping intentions, and reactions of sympathy mediated this relation. Emotional reactions and helping intentions varied based on gender of both the participant and the person in need. Study 3 added a component to the model, prior knowledge, and demonstrated that the provision of information about NSSI may alter an individual’s causal attributions, emotional reactions, and helping intentions, in beneficial ways. Overall, these findings support the potential use of a theoretical model for future research and highlight the value in provision of NSSI information as a possible outreach initiative.