Mutual regulation of anger plays a role in both healthy adjustment and mental health problems. This study of 85 preschooler boys and girls examined mother–preschooler anger regulation during a frustration in relation to the child's preschool and school age problem status. Less mutual positive emotion, more mutual anger, and more emotional mismatches than other dyads characterized dyads with a stable conduct problem child. Maternal emotion predicted school age conduct problems, particularly for boys. Maternal emotion also predicted stability versus improvement of symptoms. The emotional dynamics of mother–preschooler angry exchanges may redirect girls' conduct problems and may contribute to the stability of boys' conduct problems.