Abstract The consequences that the COVID-19 pandemic had on the mental health of adolescents are emerging and require particular attention in settings where challenges like armed conflict, poverty and internal displacement have previously burdened their mental wellbeing. We conducted a cross-sectional study with 657 school attending adolescents in a post-armed conflict area in Colombia during the COVID-19 pandemic. Mental health information was obtained though screening scales. The prevalence observed for moderate to severe depression symptoms was 30.0% (CI95%=26.5-33.7) and for moderate to severe anxiety symptoms was 18.9% (CI95%=16.0-22.1). A prevalence of probable Post-Traumatic Stress Disorder of 22.3% (CI95%=18.1-27.2) was found. The CD-RISC-25 results for resilience had a median score of 54 [IQR:30]. These findings highlight the need to strengthen mental health care systems, with schools being key places in which prompt intervention might reduce the burden of mental distress in adolescents.