The COVID-19 pandemic is having a major impact on the mental health of adolescents, leading to suicidal behaviors. However, it remains to be clarified whether the COVID-19 pandemic has changed the psychiatric profile of adolescent suicide attempters. Methods: a retrospective observational analytical study was conducted to assess age, gender and clinical characteristics of adolescents attempting suicide during the year before and the year after the global lockdown. Results: ninety adolescents (12–17 y.o.) were recruited consecutively from February 2019 to March 2021 at the emergency ward for having attempted suicide. Fifty-two (57.8%) attended before the lockdown (pre-pandemic group) and thirty-eight (42.2%) the year after (pandemic group). There were significant differences in diagnostic categories between the periods (p = 0.003). Adjustment and conduct disorders were more frequent in the pre-pandemic group, while anxiety and depressive disorders were more prevalent during the pandemic. Although the severity of suicide attempts did not show significant differences between the two study periods (0.7), the generalized linear model showed that the suicide attempt severity was significantly associated with current diagnosis (p = 0.01). Conclusions: the psychiatric profile of adolescents attempting suicide was different before and during the COVID-19 pandemic. During the pandemic, the proportion of adolescents with a prior psychiatric history was lower, and most of them were diagnosed with depressive and anxiety disorders. These diagnoses were also associated with a greater severity in the intentionality of suicide attempt, regardless of the study period.