The aim of the present systematic review was dual: 1) to systematically identify and present all qualitative research exploring caregiver/child ratio and group size in Scandinavian Early Childhood Education and Care (ECEC) for children aged 0–5 years, and 2) to synthesize the results from included studies in order to explore how the structural aspects of the ECEC setting (ratio and group size) are perceived to influence the everyday life experiences, development, and wellbeing of children. All studies exploring caregiver/child ratio and group size in ECEC in Scandinavia using qualitative methods were included. Systematic electronic searches were carried out in Socindex, PsycINFO, ERIC, Academic Search Premier, Science Citation Index, Sociological Abstracts, Cristin, Forskningsbasen, Libris, Norart, Swemed, and BIBSYS between September 2020 and February 2022. Furthermore, hand searches and snowballing strategies were used to identify relevant studies. The final selection included 12 studies in the review. The quality of all included studies was assessed independently by two review authors. After critical appraisal, the thematic analysis was conducted using data from 11 studies as one included study was deemed to be of insufficient quality. Findings within the thematic synthesis highlight ways in which group size and caregiver/child ratio influence caregiver/child interactions, children’s interactions, behavior, development, and learning as perceived by caregivers and observers and the caregivers’ perceptions on what constitutes optimal group size and caregiver/child ratio in ECEC. No study included in the review used interviews with children or parents, and thus future research is needed in order to explore children’s perspectives on these central structural characteristics of the ECEC setting.