Objective: The aim of the current study was to examine the rates of violence prior to and 3 years following treatment initiation, and predictors of post-treatment violence in Chinese young people presenting with first-episode psychosis (FEP). Method: Seven hundred patients aged 15–25 years consecutively enrolled in a territory-wide early intervention program for FEP in Hong Kong from July 2001 to August 2003 were studied. Socio-demographic, pre-treatment, baseline and 3-year follow-up variables were collected via systematic medical file review. Violent behavior was defined as physical aggression towards people and was further categorized at two levels of severity. Results: After onset of psychosis, 6.7% ( n = 47) patients exhibited violence before treatment. During 3-year treatment period, 9.4% ( n = 66) committed violent behavior and 4.3% ( n = 30) perpetrated serious violence. Two-fifths (40.4%) of patients who displayed pre-treatment violent behavior engaged in further act of violence after service contact. Multivariate regression analysis showed that previous violence, male gender and lower educational attainment were significantly associated with an increased risk of violence during 3-year follow-up. Comorbid substance, male gender, lower educational level and past history of violence were found to independently predict occurrence of serious violence after commencement of treatment for FEP. Conclusions: In a large representative cohort of Chinese young FEP patients, the rates of violent behavior before and after treatment were relatively lower than that reported in the literature. Risk factors for violence identified by the current study were comparable to the findings of previous research conducted in western populations. Close monitoring of patients with history of violence and specific treatments targeting at minimizing substance abuse may facilitate early identification and intervention of high-risk cases to reduce violence risk in the early course of illness.