The situational model of bystander behavior is a validated 5-step process for understanding intervention in bullying and sexual harassment, yet the individual-level and contextual-level factors that facilitate the progression from one step to the next are not well understood. The purpose of the current study was to examine whether individual characteristics (social-emotional skills, affective empathy, cognitive empathy, and personal attitudes toward bullying and sexual harassment) and contextual-level factors (school climate and perceived peer attitudes toward bullying and sexual harassment) explained the association between subsequent steps of the bystander intervention model. A sample of 788 high school students completed several validated measures of these constructs. Using structural equation modeling, the measurement model revealed that each step significantly and positively predicted the next step, and the addition of a direct path from accepting responsibility to helping improved model fit. The mediational model indicated that individual-level characteristics had significant direct effects on interpreting bullying and sexual harassment as problems, accepting responsibility, and helping, and indirect effects from noticing the bullying and sexual harassment to all subsequent steps. In contrast, contextual-level effects contributed to accepting responsibility in an inverse direction. [This paper was published in "Aggressive Behavior."]