Objective Non‐suicidal self‐injury (NSSI) is physically harmful behaviour, primarily used to regulate emotions. Emotion regulatory ability is theorised to develop in the context of primary attachment relationships and to be impacted by the quality of these relationships. We propose a developmental perspective for why some people engage in NSSI. Method A questionnaire assessing aspects of attachment, emotion regulation, and NSSI was completed by 237 young adults. Results Participants reporting NSSI were more likely to report difficulties in attachment relationships and emotion relation. Using multiple mediation modelling, anxiety related to mothers, and a fearful attachment model predicted NSSI through non‐acceptance of emotional responses and lack of regulatory strategies; the fearful model also predicted NSSI through difficulties in engaging in goal‐directed behaviour and impulse control. Conclusions Risk of NSSI may increase as a result of attachment difficulties and associated emotional development; early prevention measures may be useful. Treatment of NSSI should target attachment constructs as well as understanding, expression, and regulation of emotion.