Objectives Externalizing behavior problems are considered to be a serious impediment to a child’s development, and therefore it is important to identify their predictors. In this study, we investigated the connections between school-aged boys’ externalizing problems, the mother’s reflective functioning (RF) and the mother’s perception of her childhood relationship with her own caregivers. Methods The study sample comprised 39 school-age boys diagnosed with externalizing behavior problems together with their mothers. A child’s psychopathology was assessed using the Child Behavior Checklist and Teacher Report Form. Our assessment of the mothers’ mentalizing capacities was based on the Adult Attachment Interview and Reflective Functioning Scale. The perception of a mother’s childhood relationship with her parents was assessed using the Parental Bonding Instrument. Results The analysis revealed that more severe cases of aggressive and rule-breaking behavior in boys were associated with lower RF in mothers, as well as with a mother’s perception of her childhood relationship with her own parents as less autonomous. More aggressive behavior in boys was also associated with a mother’s perception of herself as experiencing a higher degree of care from her father during her own childhood. Conclusions These are only preliminary findings and we have discussed them with a view to understanding the possible ways in which a mother’s RF and the intergenerational context of relationship quality are associated with externalizing behavior problems in middle childhood.