Objective. To examine the role of infant attachment classification and parenting stress for toddler emotional and behavior problems. Design. Participants were 606 infant-mother dyads who took part in a population-based cohort study in the Netherlands. Infant-mother attachment classification was assessed using the Strange Situation Procedure when the children were 14 months old. At 18 months, parenting stress was measured with the Dutch version of the Parenting Stress Index. When the children were 3 years old, both mothers and fathers completed the Child Behavior Checklist. Results. Infant attachment moderated the effect of parenting stress on child emotional and behavior problems. Parenting stress was related to more aggression and attention problem behaviors in insecurely attached children, but not in securely attached children. Moreover, higher parenting stress was associated with more withdrawal problem behaviors in insecurely attached children, in particular in insecure-resistant and in disorganized children. Conclusion. In the presence of an insecure attachment relationship, more parenting stress is related to more (internalizing) withdrawal problem behavior and to more (externalizing) aggression and attention problems. Attachment security in infancy buffers the influence of parenting stress on child emotional and behavior problems.