Minors with and without migration background can have different risk factors and triggering reasons for self-harming and suicidal behaviour. We retrospectively analysed the data of 192 children and adolescents to investigate the transcultural differences in self-harming, as well as suicidal behaviour in Austrian, Turkish, and Bosnian/Croatian/Serbian (BCS)-speaking patients, who were treated in an emergency out-patient clinic in Vienna. Our results showed transcultural differences in both behaviours. In all groups, females had higher rates of suicide attempts and self-harming behaviour than males. While Turkish-speaking patients received treatment more often, after attempted suicide, Austrians and BCS-speaking patients needed treatment more often for acute stress disorder. Suicide attempts and self-harming behaviours were triggered most frequently by intrafamilial problems, but more frequently in migrant patients. Turkish-speaking patients were at a more than 2 times (OR = 2.21, 95%CI: 1.408–3.477) higher risk for suicide attempts, and were triggered almost 3 times (OR = 2.94, 95%CI: 1.632–5.304) more often by interfamilial conflicts. The suicide attempts of BCS-speaking minors were more often caused by relationship and separation crises (OR = 2.56, 95%CI: 1.148–5.705). These transcultural differences in suicidal and self-harming behaviour of minors, demand an increase of transcultural competence to provide optimal treatment of migrant children.