Background and Objective: UNESCO and other organisations have outlined the importance of early childcare for children’s psychological wellbeing. We aimed to investigate how the age of starting and the intensity of formal childcare in under-5s were associated with self-esteem trajectories between 11 and 17 years and life satisfaction at 11 and 14 years. Methods: Data from 5484 children from the UK Millennium Cohort Study were used. Childcare intensity (no childcare, part-time and full-time) and age of starting (0-1, 2-3, and 4-5 years) were measured between birth and 5 years. Self-esteem was self-reported at 11, 14 and 17 years, life satisfaction at 11 and 14 years. Ordered and binary logistics regression were used to analyse the association between childcare and life satisfaction, and multilevel logistics models to analyse the association between childcare and self-esteem. To understand the confounding by socio-economic position, models were first analysed unadjusted and then adjusted for socio-economic position, demographic information, maternal mental health and temperament. Results: Most results were null. In unadjusted analyses, later age of starting was consistently associated with lower odds of good life satisfaction (e.g., OR = 0.79 for children who started childcare aged 3-5 years compared to < 1 year). However, upon adjustment for family socio-economic position, effect sizes attenuated and became null (OR = 1.01). Childcare estimates were confounded as children from a lower socio-economic position started childcare later and had lower odds of good psychological wellbeing. Further investigation revealed that income was the SEP measure that confounded the association the most. The adjustments for demographic information, maternal mental health and child temperament did not alter the unadjusted estimates. Conclusions: We find limited evidence that childcare is related to life satisfaction. Evidence that children who start childcare later might have worse psychological wellbeing is likely due to positive confounding by socio-economic position.