OBJECTIVE: This study aims to describe child homicide perpetrators and estimate their global and regional proportion to inform prevention strategies to reduce child homicide mortality worldwide. DESIGN: A systematic review of 9431 studies derived from 18 databases led to the inclusion of 126 studies after double screening. All included studies reported a number or proportion of child homicides perpetrators. 169 countries and homicide experts were surveyed in addition. The median proportion for each perpetrator category was calculated by region and overall and by age groups and sex. RESULTS: Data were obtained for 44 countries. Overall, parents committed 56.5% (IQR 23.7-69.6) of child homicides, 58.4% (0.0-66.7) of female and 46.8% (14.1-63.8) of male child homicides. Acquaintances committed 12.6% (5.9-31.3) of child homicides. Almost a tenth (9.2% (IQR 0.0-21.9) of child homicides had missing information on the perpetrator. The largest proportion of parental homicides of children was found in high-income countries (64.2%; 44.7-71.8) and East Asia and Pacific Region (61.7%; 46.7-78.6). Parents committed the majority (77.8% (61.5-100.0)) of homicides of children under the age of 1 year. For adolescents, acquaintances were the main group of homicide perpetrators (36.9%, 6.6-51.8). There is a notable lack of studies from low-income and middle-income countries and children above the age of 1 year. CONCLUSION: Children face the highest risk of homicide by parents and someone they know. Increased investment into the compilation of routine data on child homicide, and the perpetrators of this homicide is imperative for understanding and ultimately reducing child homicide mortality worldwide. TRIAL REGISTRATION NUMBER: PROSPERO registration number: CRD42015030125.