The present study employed parallel analyses to develop a greater understanding of the relationships between infant socialization (maternal sensitivity and home quality), early childhood self-control (attentional focusing, inhibitory control, gratification delay, and self-control), and measures of reactive-overt and relational aggression, assessed from ages 8.5 to 15 years. Self-reported, mother reported, and observational data were employed from a national sample of N = 1364 children (the National Institute of Child Health and Human Development Early Child Care and Youth Development Study). Findings provided evidence that positive infant socialization during the first two years of life positively predicted self-control that in turn negatively predicted both reactive-overt and relational aggression at age 8.5 years. In addition, socialization factors maintained direct effects on developmental changes in both measures of aggression at age 10.5 years (relational), 11.5 years (reactive-overt and relational), and 15 years (reactive-overt and relational). Self-control also negatively predicted developmental changes in both measures of aggression at 11.5 years. These findings highlight the long-term developmental effects of positive infant socialization experiences on the developmental course of reactive-overt and relational aggression, but also the salience of self-regulatory capacities in understanding the etiology of and ongoing developmental changes in aggressive behaviors. •Infant socialization predicted self-control and aggressive behaviors•Socialization and self-control predicted developmental changes in aggression•Notable similarities for both reactive-overt and relational aggression