There are limited studies involving preschool children and phenomena such as harassment, bullying, exclusion and rejection. This study explores the relations between 4- to 6-year-old children's experiences of being frequently harassed in Norwegian Early Childhood Education and Care (ECEC) institutions, their overall feeling of subjective well-being and their social relationship experiences with staff and peers. The study also investigates whether there are significant differences between frequently harassed children's experiences of well-being and social relations compared to other children's experiences. The data reported in this study are collected through the Norwegian ECEC Well-being Monitor, an online, free of charge, electronic questionnaire developed for ECEC institutions. A total of 3598 children are included in the study. The main findings show that, for a majority of indicators, children who are frequently harassed have significantly different experiences of subjective well-being and social relations with peers and staff, mostly more negative, than other children.