Emotion expression is a central aspect of social–emotional functioning. Theorists assert that emotion expression undergoes significant changes in the preschool period. There is, however, limited observational evidence of those changes, which may vary by interpersonal context and gender. The present longitudinal study examined developmental changes in emotion expressions from ages 3 to 5 years in 120 children from rural economically strained families. Children's facial, vocal, and postural sadness, anger, and happiness expressions were observed in frustrating tasks in 3 social contexts (a perfect circles task with an experimenter, a toy wait task with mother, a locked box task when alone). Findings indicted that sadness expressions decreased with age in all 3 contexts. Anger expressions increased with age in the frustrating task with the experimenter and when alone but not with the mother. From age 4 to 5 years, happiness expressions decreased in the task with experimenter but increased when alone and increased marginally with mother. In terms of gender, girls expressed greater happiness (and lower sadness) than boys but only in the task with the experimenter. Findings suggest that sadness expressions decrease over the preschool years. Developmental changes in happiness and anger expressions (and gender differences) likely depend on context. Highlights The study examined developmental changes and gender differences in emotion expression from age 3–5 years in three frustrating interpersonal contexts. Sadness decreased, anger increased with the experimenter and alone (but not with mother), and happiness decreased with the experimenter. Findings suggest declines in sadness expressions, but that anger and happiness expressions are selectively expressed to fit contextual demands.