The aim of the study was to assess whether a parent's psychological well-being and/or self-efficacy relate to interaction within the family. This study is part of a Finnish follow-up study called Steps to the Healthy Development and Well-Being of Children (STEPS;). The study group included 120 families. Mother's and father's social anxiety and depression were assessed during pregnancy and at 18 months of the child's age using self-report questionnaires; the mother's and father's self-efficacy were assessed at 18 months using a parental self-efficacy scale validated within the STEPS study. Mother-father-child triadic interaction was studied at 18 months within a Lausanne Triadic Play setting. Results showed that maternal symptoms of depression during pregnancy and maternal social anxiety at 18 months were related to triadic interaction within the family. There was no relation between father's psychological well-being and triadic interaction within the family. Father's self-efficacy in teaching tasks and the Mother's self-efficacy in emotional support were associated with family interaction. The findings suggest that maternal psychological well-being and self-efficacy in emotional support may be important components of family triadic interaction whereas paternal self-efficacy in teaching tasks seems to support family coordination in triadic interaction.