New migrants from Mainland China to Hong Kong have faced increased discrimination from local Hong Kongers, which may have negative impacts on their adjustment and mental health. Guided by the family systems theory, we tested the dyadic effects of perceived discrimination levels among migrant children and mothers on their psychological distress in a sample of 200 child–mother pairs who migrated from Mainland China to Hong Kong. Using polynomial regression and response surface analyses, we found that when children's and mothers’ reports of perceived discrimination showed congruence, higher levels of perceived discrimination were positively associated with both children's and mothers’ psychological distress. In addition, when children's and mothers’ reports of perceived discrimination were discrepant, higher levels of perceived discrimination among children compared with mothers were associated with increased psychological distress for children, and higher levels of perceived discrimination among mothers compared with children were associated with increased psychological distress for mothers. By using a dyadic approach, our study advances the understanding of the degree to which child–mother congruence and the direction of discrepancies in perceived discrimination contributes to children's and mothers’ psychological distress. These findings have implications for the design of psychological distress‐reduction intervention programs in the context of discrimination among migrant pairs.