Attachment theory provides a frame for understanding the role of attachment styles in the development of bullying behaviour in adolescence. The present study examined attachment styles (secure, avoidant and anxious/ambivalent) that differentiated bullies, victims, bully/victims and uninvolved adolescents. A total of 1,921 students (1,006 girls and 915 boys) in grades four through nine (ages 10 to 18 years old) completed a peer-reported measure (peer nomination inventory: D. G. Perry, Kusel, & L. C. Perry, 1988) to determine the status of bullying behaviour (bullies N = 178; victims N = 168; and bully/victims N = 16) and a self-reported measure to examine attachment style (multiple-item attachment scale: Simpson, 1990). A one-way ANOVA indicated that: (1) Bullies had higher scores in avoidant attachment scales than victims and non-participants of bullying; and (2) Victims demonstrated higher levels of insecure attachment than bullies and uninvolved adolescents. Findings reflected the role of insecure attachment as a risk factor in the development of bullying behaviour in adolescence--bullies were at risk when their current attachment styles were avoidant and victims when their attachment styles were insecure. (Contains 3 tables.)