The current research produces regression models with sample sizes from 127 to 131 by initially employing a data set of 170 nations. The current study finds that ethnic heterogeneity and linguistic heterogeneity lead to higher homicide rates. However, religious heterogeneity has no impact on homicide rates. The present article also tests an interaction effect between population heterogeneity and income inequality. Unlike J. R. Blau and Blau (1982) and Avision and Loring (1986) proposition, the interaction term is not related to national homicide rates. The current study also discusses the theoretical implications of those findings.