Introduction Adolescent aggression leading to crime is a growing global issue, and understanding its antecedents is crucial. Previous studies have shown that hostile attribution bias and difficulties in emotion regulation are significant psychological factors influencing aggression. However, traditional interventions are limited by time and space constraints. Online contextual interventions offer flexibility but have remained underutilized in this field. This study examines the predictive role of hostile attribution bias and difficulties in emotion regulation in adolescent aggression and explores the impact of online interventions on reducing these biases, assessing their potential for preventing adolescent crime. Objective The study aims to first verify the significant predictive role of hostile attribution bias and emotion regulation difficulties in adolescent aggression. Secondly, it seeks to explore whether online contextual interventions effectively reduce hostile attribution bias and improve emotion regulation ability, ultimately aiming to reduce aggression and prevent crime. Methods This research consists of two studies. Study 1 involved a survey of 559 adolescents from Wenzhou, China, using the Adolescent Aggression Questionnaire, Hostile Attribution Bias Scale, and Difficulties in Emotion Regulation Scale. Pearson correlation, regression analysis, and mediation tests were employed to analyze the data. Study 2 employed a randomized controlled design, dividing participants into experimental and control groups. The experimental group received online interventions targeting hostile attribution and emotion regulation ability, while the control group viewed unrelated documentaries. Post-intervention, both groups were reassessed, and independent sample t-tests were used to evaluate the effects. ResultsStudy 1 showed that hostile attribution bias (r =.577, p <.001) and emotion regulation difficulties (r =.630, p <.001) significantly predicted adolescent aggression, explaining 50.6% of the behavioral variance (R-2 = 0.506). Study 2 demonstrated a significant reduction in hostile attribution bias (M = 55.15, SD = 18.35, t = 3.05, p =.010) and emotion regulation difficulties (M = 33.46, SD = 14.02, t = 4.81, p <.001) in the experimental group post-intervention, while the control group showed no significant changes. Conclusions(1) Hostile attribution bias and emotion regulation difficulties significantly predict adolescent aggression; (2) Online contextual interventions effectively reduce hostile attribution bias and improve emotion regulation abilities in adolescents; (3) The study provides theoretical and empirical support for using online interventions in behavioral correction and crime prevention in adolescents; (4) Online interventions offer a convenient, efficient approach to preventing aggression and crime among adolescents. Clinical trial numberThis study was retrospectively registered in the Chinese Clinical Trial Registry (ChiCTR2500100303, registration date: April 7, 2025).