Victimization and perpetration of cyberbullying and traditional bullying are prevalent among adolescents with autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). The aims of this study were to examine the role of social anxiety in victimization and perpetration of cyberbullying and traditional bullying in adolescents with ASD and ADHD in Taiwan. A total of 219 adolescents with ASD and 287 adolescents with ADHD aged 11-18 years and their caregivers were recruited from the child psychiatry outpatient clinics into this study. The associations of social anxiety with victimization and perpetration of cyberbullying and traditional bullying were examined using logistic regression analysis. The results indicated that after the effects of sex, age, and autistic social impairment were controlled, social anxiety increased the risk of being a victim of cyberbullying (Odds Ratios (OR) = 1.048; 95% Confidence Interval (CI): 1.013-1.084), a victim of traditional bullying (OR = 1.066; 95% CI: 1.036-1.097), and a perpetrator of traditional bullying (OR = 1.061; 95% CI: 1.027-1.096) in adolescents with ASD. After the effects of sex, age, and ADHD symptoms were controlled for, social anxiety increased the risk of being a victim of traditional bullying in adolescents with ADHD (OR = 1.067; 95% CI: 1.039-1.096). Social anxiety was significantly associated with several forms of bullying involvement in adolescents with ASD and ADHD and warrants being considered into prevention and intervention programs for bullying involvement.