The prevalence rate of individuals with autism spectrum disorder (ASD) is increasing. One of the main deficits among people diagnosed with ASD is the presence of stereotypy. More importantly, stereotypy are difficult to reduce because they are often maintained by automatic reinforcement and do not have clear antecedent or trigger to these behaviors. Most interventions that are often used to address stereotypy are consequence- and punishment-based interventions, such as response interruption and redirection and response blocking. Although these interventions are effective in reducing stereotypy, they are only implemented after the stereotypy are exhibited and practitioners need to be trained to implement these interventions. In addition, they may produce negative behavioral side effects, such as tantrum behaviors and aggression. Consequently, more research has been focusing on developing antecedent-based interventions on reducing stereotypic behaviors that would also prevent negative side effects. Recent research have indicated that antecedent physical exercise interventions can lead to significant reduction of stereotypy and also many other positive collateral effects, such as increased level of academic engagement. However, various types of exercises have been incorporated in previous research and there is not enough evidence to suggest which type of physical exercise interventions or specific intervention parameters yield the largest reduction in stereotypy. Therefore, the purpose of this study was to investigate the effects of varying antecedent exercise intensities and examine whether exercise intervention with higher intensity are more effective in reducing stereotypic behaviors than lower intensity exercise intervention. In addition, this study examined participants’ subsequent task engagement or functional play as collateral effects. Results indicated that children with ASD who engage in stereotypy can benefit from antecedent exercise regardless of the exercise intensity. However, the findings suggested that higher intensity antecedent exercise led to lower levels of subsequent stereotypy and higher levels of other adaptive behaviors when compared to lower intensity antecedent exercise. Potential implications and recommendations for practitioners working with children with ASD who engage in stereotypy are provided, in addition to possible areas of future research.