Prior research suggests that young children display higher cortisol levels in out-of-home childcare than at home. Social competence, such as prosocial or antisocial behavior, may affect stress regulation in a peer group setting. The aim of this study was to compare diurnal cortisol levels at home and in out-of-home childcare and examine the association between cortisol and child social competence. We hypothesized that differences in cortisol levels between home- and childcare day diminish along with child age from 2 to 5 years. Further, we assumed that lower prosocial and higher antisocial behavior would be positively associated with total diurnal cortisol in out-of-home childcare. A total of 108 children were drawn from the FinnBrain Birth Cohort Study. Four saliva cortisol samples were collected over two consecutive days (home day and childcare day) at 2, 3.5 and 5 years. Mothers reported child social competence by responding to Multisource Assessment of Child Social Competence at the age of 5. Contrary to expectations, total diurnal cortisol was not associated with child social competence. There were neither difference in cortisol levels between the home- and childcare day at the age of 5. Our earlier findings on the same study population showed higher afternoon cortisol levels during the childcare day at 2 and 3.5 years. However, such difference was no longer observed at the age of 5. More experience in out-of-home childcare, developed social competence and more matured self-regulation may explain the lack of such differences. Longitudinal analyzes are currently being examined.