The study examined the prevalence and nature of bullying behaviour among secondary school students in Nigeria. It also investigated the factors associated with bullying and its psychological consequences. The study adopted a survey design. A sample of 750 secondary school students was selected through stratified random sampling technique using sex, age and class level as strata from five randomly selected secondary schools in Ile-Ife, Osun State, Nigeria. Information was collected from the students through the administration of an instrument titled “Bullying Behaviour Questionnaire” (BBQ). Results showed that the prevalence of bullying among the students was 67.2%. From this, 88.1% had been bullied and 33.1% were bullies. Many students (64.7%) had been involved in relational bullying. Watching violent films (57.5%) and retaliation for being bullied in the past (51.2%) were some of the factors associated with bullying. The bullied students exhibited fear (63.6%) and depression (58.1%).