Suicide is an important social and medical problem, particularly among children and adolescents. The aim of the study was to determine the association of the psychiatric diagnosis and selected psychosocial factors with the risk of suicide attempts among patients of an adolescent psychiatric unit. A retrospective analysis was performed on a database of consecutive N = 1311 patients aged 13–18 years of the adolescent psychiatric ward. A hierarchical logistic regression analysis was performed to assess the predictive value of the main psychiatric diagnosis, for factors selected from the database to determine their influence on the relative risk of a suicide attempt. Primary diagnoses of mood disorders and emotional and behavioral disorders were associated with an increased risk of a current admission after a suicidal attempt, a history of past suicidal attempts and non-suicidal self-harm (NSSI). History of NSSI was associated with a fourfold increase probability of a suicide attempt. Truancy, sexual abuse, heartbreak and frequent conflicts were related to a rise in suicidal attempt risk. Learning difficulties were found to be linked to increased probability of suicidal attempt, but only among women. The current study confirms that the primary diagnosis, NSSI and well-recognized psychosocial factors (including family- and school-related factors) may prove useful in the assessment of suicidal risk among adolescents admitted to a psychiatric ward.