This study aimed to determine the prevalence of deliberate self-harm (DSH) among adolescents in England and the factors associated with it. A cross-sectional survey using an anonymous self-report questionnaire was conducted in 41 schools, involving 6020 pupils aged 15 and 16 years. The results showed that 398 participants (6.9%) reported DSH in the previous year, with only 12.6% of episodes resulting in hospital presentation. DSH was more common in females (11.2%) than in males (3.2%), with odds ratios indicating a strong gender difference. Multivariate logistic regression identified several factors associated with DSH in both genders, including recent self-harm by friends, self-harm by family members, drug misuse, depression, anxiety, impulsivity, and low self-esteem. The study concluded that DSH is common in adolescents, particularly females, and emphasized the need for school-based mental health initiatives to address this issue. These initiatives could include education about mental health problems and screening for at-risk students.This study aimed to determine the prevalence of deliberate self-harm (DSH) among adolescents in England and the factors associated with it. A cross-sectional survey using an anonymous self-report questionnaire was conducted in 41 schools, involving 6020 pupils aged 15 and 16 years. The results showed that 398 participants (6.9%) reported DSH in the previous year, with only 12.6% of episodes resulting in hospital presentation. DSH was more common in females (11.2%) than in males (3.2%), with odds ratios indicating a strong gender difference. Multivariate logistic regression identified several factors associated with DSH in both genders, including recent self-harm by friends, self-harm by family members, drug misuse, depression, anxiety, impulsivity, and low self-esteem. The study concluded that DSH is common in adolescents, particularly females, and emphasized the need for school-based mental health initiatives to address this issue. These initiatives could include education about mental health problems and screening for at-risk students.