Nonsuicidal self-injury (NSSI) and suicidal behavior (SB) have a significant prevalence in transsexual people. The published data is confusing as it does not distinguish between ideation and realization, age groups, gender, or the degree of medical intervention. Their actual prevalence in Spain is unknown. Our objective was to investigate the prevalence of NSSI behavior and SB in adolescents and young transsexual adults, differentiating between ideation and consummated behavior, prior to their receiving any type of gender-affirming medical treatment. We retrospectively reviewed the medical history of a cohort of transsexual people aged between 10 and 35 years, treated at the Gender Identity Unit of the Valencian Community. We analyzed the data collected regarding the presence of four variables: NSSI ideation, NSSI behavior, ideas of suicide and suicide attempts, as well as differences according to age group and gender. The final sample consisted of 110 transsexual men and 90 transsexual women. Of these, 21% had made a suicide attempt, 50% had had suicidal ideas, 31% had a history of NSSI behavior and 35% had had NSSI ideas. No differences were found based on gender. Regarding age, subjects under 20 years of age presented a significantly higher prevalence regarding suicidal ideas compared to young adults (43% vs. 25%), while in the remaining variables, no statistically significant differences were found. The prevalence of a history of suicidal ideas and behavior in the Spanish adolescent and young transsexual population is significant and does not differ according to gender or age range. The prevalence of NSSI ideas and behavior differs and is more frequent in adolescent transsexuals. Copyright © 2020 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.