Aim: Studies of children’s early ability to communicate have mainly focused on mother-child dyads. That is why this study analysed the long-term effects of triadic interactions involving both parents. Method: This prospective pilot study monitored child-mother-father communication in 19 families from the general population in Sweden using the standardised Lausanne Trilogue Play method in a video studio. The families and their first-born child were initially followed from three months to 48†months of age. Preschool teachers assessed the children at the age of four using the Preschool Behaviour Questionnaire and then their teachers assessed the subjects at the age of 15 using the Strengths and Difficulties Questionnaire. Early communication was analysed in relation to the children’s social competence at the age of†15. Results: The child’s skills in initiating turn-taking sequences and their parents’ responses to this correlated with the child’s social competence at the age of four, as reported in a previous study from our group, and at the age of 15, as reported here. Conclusion: The results of this study indicated that stimulating children’s capacity to initiate turn-taking sequences in infancy improved their social competence at the age of 15, confirming positive results at four years of age. ©2018 Foundation Acta PÊdiatrica. Published by John Wiley & Sons Ltd