The current study investigated developmental trajectories of teacher-reported aggressive behavior and whether these trajectories are associated with social-cognitive development (i.e., aggressive problem-solving) across the first three elementary grades in a large sample from Switzerland (N = 1,146). Semiparametric group-based analyses were employed to identify distinct pathways of aggressive behavior across grades. Five distinct trajectory classes were identified: low-stable, medium-stable, decreasing, increasing, and high-stable. Children's aggressive problem-solving strategies differentiated the high-stable from the other aggressive behavior trajectories. The findings are discussed within a social-cognitive developmental framework.