Bullying is an emerging serious problem in schools worldwide resulting in physical and mental health problems in victimized children. Teachers play a critical role in identifying the acts of bullying, assisting the children who are victimized, linking up with healthcare providers for managing physical and emotional consequences of bullying, as well as managing bullying at school.To determine teachers' knowledge regarding bullying among secondary school children.A cross-sectional study conducted in five public and five private schools of Jamshed Town, Karachi, Pakistan.The study continued from October 2012 to February 2013. Stratified random sampling was used to select teachers. Data were collected through a pre-piloted structured questionnaire.Data were analyzed using the SPSS v19.0. Descriptive analysis was done by calculating frequencies and percentages of the categorical variables such as teacher's age, educational level, and presence of adequate knowledge regarding bullying. The outcome variable of interest was knowledge about bullying.Almost half of the153 teachers ( = 82, 53.6%) lacked adequate knowledge about bullying in school children. A statistically significant association was present between knowledge of bullying with gender (-value = 0.02), educational level of the teachers (-value = 0.05), years of teaching experience (-value = 0.04), and educational training of teachers (-value = 0.01).More than half of the teachers were deficient in their knowledge about bullying in school children.