Background: Adolescence is an important point in the emotional development of young people. It is a time when young people are characterised by a high degree of emotional instability and seek effective ways to regulate their emotions. One of the frequent methods they use to cope with emotional tension is self-injurious behaviour. Methods: In the context of the rising incidence of self-harm among adolescents, this study aims to understand the association of temperament with the experience of tension and self-injurious behaviour along with the mediating role of perfectionism among 366 adolescents aged 15 to 20 years (Mage = 17.98, SD = 1.302, 52.7% female). Participants completed questionnaires on temperament traits, level of perfectionism, and experience of tension and self-injurious behaviour. Results: The results show that traits such as perfectionism, sensory sensitivity and emotional reactivity increase the risk of self-injurious behaviour. Maladaptive perfectionism partially mediates the relationship between these traits and the tendency to experience emotional tension. A temperament profile with a protective role was also identified. Conclusions: The results of the study highlight the importance of innate traits as well as environmental and cognitive influences, and may contribute to a better understanding of the mechanisms leading to self-injurious behaviour and strategies aimed at its prevention.