The organization of children's secure base behaviour was studied in two-parent Portuguese families, with 44 father–child and mother–child dyads, children's age was on average 31.91 months. An analysis of Attachment Q-sort (AQS; Waters, ) data revealed no significant differences in security scores for mothers and fathers. Both parents independently responded to a questionnaire about their participation in child-related activities, relative to their spouse's participation in these activities. A traditional division in the Care/Organization tasks and a shared participation in the Play/Leisure activities emerged. Fathers with higher scores for both types of activities tended to have children with higher security scores. Fathers' participation in Play/Leisure activities was associated with children's AQS scores with their mothers. In this sample father's participation is positively associated with the quality of secure base relationships within the family context.