Background <p>It has been reported that self-harm behaviour and suicidal ideation are more prevalent among adolescents with gender dysphoria compared to the general adolescent population. However, studies examining whether these risk behaviours differ according to sex assigned at birth are limited. This study aimed to investigate whether self-harm behaviour, suicidal ideation, and severity of suicidal behaviour differ according to sex assigned at birth in adolescents diagnosed with gender dysphoria.</p> Method <p>This cross-sectional study included 32 adolescents aged 12–18 years who presented to the child and adolescent mental health outpatient clinic of a city hospital between March and October 2026 and were diagnosed with gender dysphoria according to DSM-5 diagnostic criteria. The K-SADS-PL, a semi-structured clinical interview tool, was administered to assess psychiatric comorbidities in participants. Self-harm behaviours were assessed using the Inventory of Statements About Self-Injury (ISAS), and suicidal behaviour was assessed using the Suicide Behaviour Questionnaire (SBQ). Group comparisons according to sex assigned at birth were performed using non-parametric statistical methods.</p> Findings <p>Twenty-six (81.2%) of the adolescents participating in the study were assigned male at birth, and 6 (18.8%) were assigned female at birth. Mood disorders were found in 65.6% of the sample and anxiety disorders in 78.1%; the distribution of these psychiatric comorbidities did not show any significant differences according to sex assigned at birth. Non-suicidal self-harm was reported in 62.5% of participants, with no difference in prevalence between genders. However, the severity of self-harm was significantly higher in female adolescents. Suicidal ideation was found in 50% of the entire sample; while suicidal ideation was reported in all female adolescents (100%), this rate was 38.5% in male adolescents. Furthermore, suicide behaviour severity scores were found to be significantly higher in female adolescents.</p> Conclusion <p>This study shows that suicidal ideation and suicide behaviour severity may be higher in adolescents with gender dysphoria, particularly in those who are assigned female at birth. The findings suggest that sex assigned at birth may be an important factor to consider in the clinical assessment and follow-up of adolescents with gender dysphoria in terms of suicide risk. Further studies with larger samples are needed to confirm these findings and to elucidate in more detail the biopsychosocial factors that influence suicide risk in young people experiencing gender dysphoria.</p>