Defense Style Questionnaire (DSQ) is a self-report instrument designed to measure defense mechanisms. Although commonly used, the DSQ-40 has not been validated in early adolescent populations. The present study sought to determine the factor validity of the DSQ-40 in a sample of Greek primary school students (N = 265). Further, it aimed to investigate the relationship between defense mechanisms and perceived parental acceptance/rejection, the participation in bullying (either as bully or victim) as well as self-reported well being. Participants completed the Greek version of DSQ-40, adapted for use by this particular age group as well as measures in order to examine its convergent and discriminant validity. The findings support a four-factor solution as the most adequate for our data. Further, it was found that defense mechanisms are related to perceived parental acceptance and rejection. Finally, the results showed that the DSQ-40 can effectively discriminate participants with high/low bullying/victimization and perceived well-being. Our results indicate that the DSQ-40 is appropriate for use in late childhood. Implications for clinical practice and future studies that would confirm the appropriateness of the scale’s use in younger populations are also discussed.