During the toddler period, children begin to shift from being primarily dependent on parents to regulate their emotions to managing their emotions independently. The present study considers how children's propensity towards negative emotional arousal interacts with mothers' efforts to socialize emotion regulation. Fifty-five low income mothers and their 2-year-old children completed observational assessments measuring mothers' socialization of emotion regulation, children's reactivity propensity, and children's emotion regulation. Children's propensity towards negative reactivity significantly interacted with mothers' use of physical soothing. That is, mothers with less reactive children who used more soothing had children who were more likely to use interactive, distraction-based regulatory behaviors during a frustration situation. Theoretical and child care implications of the finding are discussed.