Objective: This study assessed the mediating role of trauma symptoms in the relation between child maltreatment and behavioral problems. It is based on the postulate that child maltreatment is a severe form of chronic relational trauma that has damaging consequences on the development of children's behavioral regulation. Method: Participants were 34 maltreated and 64 non-maltreated children (mean age = 60 months; range: 46 to 72 months), all from economically disadvantaged families. Maltreated children were recruited from the Child Protection Agencies. Behavioral problems and trauma symptoms were evaluated by the preschool teacher with the Internalizing and the Externalizing scales of the Child Behavior Checklist-Teacher Report Form (CBCL-TRF) and the posttraumatic stress score of the Trauma Symptoms Checklist for Young Children respectively (TSCYC). Results: Baron and Kenny's mediational procedure was conducted using structural equation modeling. Mediational analyses revealed that trauma symptoms fully mediated the association between maltreatment and both internalizing and externalizing behaviors. Conclusions: Results were consistent with the literature on developmental trauma research and provide empirical support to the idea that trauma-related symptoms resulting from early maltreatment may constitute a mechanism in the development of psychosocial problems in preschoolers. Practice implications: These findings underline the importance of understanding psychosocial maladjustment of maltreated children not only from the perspective of problematic behavior, but also by taking into account the traumatic reactions that might develop in response to chronic and intense stress associated with abuse and neglect. (Contains 3 tables and 1 figure.)