The study aimed to determine the forms of aggressive behavior on a child at school and home. In addition to know the cause of aggressive behavior on a child. The method of this study is case study. Subject of research was a six-year-old boy (A) showing aggressive behavior. Data were collected by observation and interview. Observation conducted inside and outside the classroom. Interview conducted on teachers, parents and caregiver. Result of the study showed that behavior forms of the subject included verbal aggression (yelling, mocking and sticking out tongue) and non verbal aggression (hitting, kicking and pushing). Causal factors of aggressive behavior on the subject due to learning, reinforcement and direct experience.