Aims: Familicide is a multiple-victim homicide incident in which the killer’s spouse and one or more children are slain. A systematic review was conducted to reveal the background factors of western homicide perpetrators. Methods: The systematic search was performed in the Arto, Medic, Cinahl, Medline, EBSCOhost Academic Search Premier and Social Services abstracts databases. The keywords were familicide, family homicide, familicide-suicide, filicide-suicide, extended suicide, child, murder, family, filicide and infanticide. The searches revealed 4139 references from the databases. The references were filtered and 32 peer-reviewed research articles revealed in years 2004–2014 were selected as data. The articles were analysed using inductive content analysis, by finding all possible background factors related to homicide. Results: The factors were described as percentages of the range. The background factors of familicide perpetrators were categorised as follows: perpetrators who had committed homicide of a child and intimate partner and possibly committed suicide; a father had who killed a child; a mother who had killed a child; a father who had committed a filicide-suicide; and a mother who had committed a filicide-suicide. Conclusions: Psychological instability, violence and crime were found in all these categories of familicides. Perpetrators who had committed a suicide in addition to the familicide had more often been diagnosed with depression, but they sought treatment for mental health problems less often and had violence and self-destructiveness less often in their background than in other familicide categories. Social and healthcare professionals should be more sensitive to emerging family problems and be prepared for intervention.