In recent years, the phenomenon of street gangs has attracted the attention of the public, authorities and researchers, due to the criminal productivity and violence of its members. It is well established in the literature that young offenders associated with street gangs have more prolific and serious delinquency than young non-associated offenders, however, their individual differentiation isn’t well known. Yet, in order to optimize prevention and intervention measures, a thorough knowledge of the psychological characteristics of young offenders associated with street gangs is necessary. The objective of this study is to compare young offenders associated or not with street gangs on the basis of their personality traits, an individual characteristic closely related to delinquency. Two hundred eleven young offenders (79 of them associated with street gangs) recruited from different detention centers, as well as from youth centers in Quebec have answered multiple self-reported questionnaires (belonging to street gangs, delinquency and personality traits). Young offenders associated with street gangs are distinguished from non-associated youth offenders by a lower level of agreeableness, trust, straightforwardness, altruism, compliance, modesty and warmth, and a higher level of hostility. Beside corroborating the severity of offender’s delinquent behaviors, the study also found differences in their psychological characteristics.