Externalizing disorders (ED) refer to behaviours of a child/adolescent that negatively affect persons external to them. So far, no large-scale study on ED in adolescents attending secondary schools has been carried out in Albania. The current study explored gender and age differences in relation to externalizing disorders (ED) in a large sample of adolescents in 8 secondary schools situated in Tirana, the capital of Albania. The study adopted a mixed-methods approach. A survey consisting of two questionnaires SDQ-T and WOST were completed by 42 teachers (randomly selected) on 614 pupils randomly selected in their K7-9 classes. The teachers were divided in 4 groups which participated in one focus group meeting. Gender-related differences confirmed previous studies that indicate a higher prevalence of ED in the male population. Evidence on age-related differences was mixed, with quantitative data indicating higher levels of ED in the 14 and 15-year olds in comparison with the 13-year olds, and qualitative data suggesting the opposite trend, that is, higher levels in 13-year olds attending year 7 adjusting to transition in secondary schools, gradually decreasing in years 8 & 9. Recommendations based on the findings of the study are given regarding interventions that should target coping with school transitions in secondary school, promoting positive social skills and competencies, emotion regulation techniques and awareness of risks related to unsupervised use of social apps/media in schools.