This study reviews the European evidence on the impact of professional development (PD) of pre-school educators on child outcomes. A meta-analysis investigates how PD of pre-school educators in formal pre-school centers in Europe affects child outcomes. The European studies are quite recent and limited in numbers, and our results show a significant positive effect of PD on child outcomes with an overall effect size of 0.35 (with a 95% confidence interval from 0.20 to 0.51). The magnitude is slightly smaller than corresponding results based on US studies, but indicates a general positive effect of PD on child outcomes.