Anger-related traits are regulated by genes as well as early environmental factors. Both childhood maltreatment and genes underlie vulnerability to suicidal behaviors, possibly by affecting the constitution of intermediate phenotypes such as anger traits. The aim of this study was to test the interaction between nine candidate genes and childhood maltreatment in modulating anger-related traits in 875 adult suicide attempters. The State-Trait Anger Expression Inventory and the Childhood Trauma Questionnaire were used to examine anger traits and traumatic childhood experiences, respectively. The functional polymorphism of the catecholamine-O-methyl-transferase (COMT) gene Val158Met significantly modulated the association between sexual abuse and anger-trait level (P = 0.001). In the presence of sexual abuse, individuals carrying the Val high-activity allele displayed greater disposition toward anger than individuals homozygous for the Met allele (P = 0.0003). Notably, none of the serotonin-related genes influenced the effect of childhood abuse on anger traits. The results of the present study suggest that anger-trait level is influenced by the interaction between childhood abuse and functional polymorphism in the COMT gene. This study was carried out in a population with a high frequency of childhood abuse and a high disposition toward anger, and replication in healthy subjects is needed.