Previous studies of emotion regulation in young children commonly used between-person approaches, which limit our understanding of dynamic and temporal relations between emotion expressions and strategy use. Further, previous work has mainly focused on temperamental reactivity among White children, and it is unclear whether these findings can generalize to children of Asian and Latinx origins. In the current study, we examined the within-person temporal associations between emotion expressions and strategy use among 3- to 5-year-old children in low-income Chinese American (CA) and Mexican American (MA) families. Children’s emotion expressions (positive and negative) and strategy use (gaze aversion, self-soothing, fidgeting, and language) during an unfair social interaction task were coded by 10-s epoch. Executive functions were examined as between-person level predictors of strategy use. Multilevel modeling was conducted to examine whether positive and negative emotion expressions at one epoch (t − 1) predicted strategy use at the following epoch (t). The results indicate that positive emotion expressions predicted an increase in fidgeting at the next epoch (β = .34, p < .01). Executive functions were unrelated to strategy use. Cultural group differences were found: CA children displayed lower intensity of positive emotion and fewer strategy use compared with MA children. The present findings inform theories on the dynamics of emotion regulation in young children and have implications for interventions with underrepresented immigrant populations.