Children with autism spectrum disorder exhibit challenges in regulating negativity and modifying emotional responses, a process known as emotion regulation. Such challenges affect social outcomes and response to intervention in children with autism spectrum disorder. Caregivers of children with autism spectrum disorder facilitate children's emotion regulation through a process known as co-regulation, but there have been no attempts to describe how dyadic use of strategies interact to impact the likelihood of negativity in real time. This study used video observations of 71 toddlers (mean age = 31.2 months) with autism spectrum disorder and their caregivers engaged in a frustrating, goal-oriented task. A mixed-effects logistic regression revealed that caregivers' use of co-regulation strategies was not a significant predictor of changes in the likelihood children's expressed negativity. Caregiver unresponsiveness and proactiveness, however, predicted increased likelihood of children's subsequent negativity. Children's use of high energy, non-instrumental behaviors (tension release), was also a robust predictor of increased likelihood of subsequent negativity. These findings shed a light on the effectiveness of child and caregiver strategies in facilitating emotion regulation in toddlers with autism spectrum disorder.