Research on school bullying often focuses on the directional path of bullying and/or victimization leading to psychosocial problems, while such one-dimensional views have been shown to be too simplistic. Furthermore, recent research has shown that patterns of bullying at school differ for boys and girls, which makes gender a particularly relevant factor in exploring the causes and consequences of bullying. Therefore, the present study explored the bidirectional, longitudinal associations of bullying and bullying victimization on several psychosocial problems via a longitudinal cross-lagged panel study in 1243 adolescents in the Netherlands, while taking into account potential gender differences. Data were collected in September 2011 and 2012. Results showed that both bullied boys as well as girls reported more conduct problems at follow-up. Both boy and girl bullies reported less pro-social behavior and more peer problems at follow-up, but boys also reported more conduct problems at follow-up, while girls did not. Furthermore, in girls, emotional problems were associated with more victimization at follow-up, while inattention-hyperactivity problems and less pro-social behavior were related to increased chances of being a perpetrator of bully at follow-up. Conversely, in boys, baseline inattention-hyperactivity problems were not associated with being a bully later on, but rather with increased chances of being a bullying victim at later times. These results can help to tailor future anti-bullying interventions at schools.