Adolescent bystanders (i.e., witnesses to violence) can prevent sexual and dating violence among their peers and create a safer social environment if they detect the opportunity. The current study prospectively examined the association of demographic (i.e., age, gender, sexual orientation), psychosocial (i.e., knowledge, rape myth acceptance, victim empathy), and behavioral (i.e., binge drinking) factors with bystander opportunity detection in situations regarding sexual and dating violence among adolescents ( N = 1,322, 50.3% girls/women, 88.9% White/non-Hispanic, 85.9% heterosexual, 18.6% free/reduced lunch, aged 13–19). Sexual minority girls, adolescents with greater victim empathy, and binge drinkers were more likely to detect bystander opportunity than heterosexual girls, boys, adolescents with less victim empathy, and nonbinge drinkers. These findings suggest that current theoretical frameworks used to understand bystander opportunity and action may be enhanced by the consideration of demographic and personal characteristics.