The present study aimed to explore children’s and adolescents’ profiles of reactive and proactive aggression and the stability of those profiles over a six-month period using latent profile analysis (LPA) and latent transition analysis (LTA). Data were collected at two measurement points from a sample of N = 1468 children and adolescents aged from 9 to 18 years. Results of LPA revealed three distinct profiles, labeled as “Severe Reactively and Proactively Aggressive (S-RA-PA)”, “Highly Reactively and Proactively Aggressive” (H-RA-PA), and “Moderately Low Reactively and Proactively Aggressive” (M-RA-PA). All profiles appeared to be relatively stable over six months, supporting their within-sample consistency. The most stable and largest profile was the “M-RA-PA” profile, while the least stable and smallest profile was the “S-RA-PA” profile. However, there was also some within-person variability in children’s and adolescents’ profile membership because almost 40–50% of the participants of the “S-RA-PA” and “H-RA-PA” profiles transitioned to another profile across six months. In contrast, more than 90% of the participants of the “M-RA-PA” profile remained in their profile. These results provide a dynamic picture of children’s and adolescents’ development of reactive and proactive aggression and bear several implications from a short longitudinal person-oriented perspective.