Introduction: Reported rates of non-suicidal self-injury (NSSI) differ by gender but may be under-reported and under-recognised in men. People engaging in NSSI rarely seek professional help without encouragement, so others play a key role in its identification and potential intervention. The current research investigated others’ interpretations of NSSI, examining whether gender affects the likelihood of NSSI identification and views of how common and acceptable NSSI is. Method: Participants (N = 429; 74.1% female, 23.3% male; please see below for further demographic information) responded to two vignettes describing a person self-injuring by punching a wall or by cutting themselves. The person’s gender in each vignette was manipulated. Following each vignette, the participants rated the level to which they agreed the behaviour was common for the gender of the person described, as well as the level to which they agreed the behaviour was acceptable for the gender of the person described, on a 5-point Likert scale. Following both vignettes, participants were presented with a definition of NSSI and rated the level to which they agreed cutting and wall-punching were forms of NSSI on 5-point Likert scales. Independent-samples t tests and goodness of fit χ2 tests were conducted as appropriate. Results: Participants were more likely to identify wall-punching as common for men and cutting as common for women. However, there was no significant difference in whether wall-punching was identified as NSSI or considered to be an acceptable behaviour, regardless of the gender of the person engaging in it. That is, although research suggests that men are far more likely to engage in wall-punching as a form of NSSI than women, participants did not recognise this. Overall, the results indicated a gender-dependent difference in how acceptable and common NSSI is thought to be, but no noticeable difference in identification of a behaviour as NSSI. Wall-punching, typically a form of NSSI engaged in by males, tended not to be identified as such. Conclusion: There is an effect of gender on how NSSI is interpreted, and it seems that men’s NSSI is, and will continue to be, under-recognised. This has important implications for the treatment of men’s NSSI, which is more likely to be seen as aggression and therefore deserving of punishment than an attempt at emotion regulation.