This article introduces and conceptually underpins an instrument to measure group functioning in child care groups, the Group Functioning Instrument for Child Care (GFI-CC). This instrument was applied in 44 Dutch child care groups (0- to 4-year-olds). The results of this first explorative investigation with the GFI-CC provided initial support for an underlying conceptual model of group functioning in child care centers based on cohesion (network structure, action coordination, and involvement) and emotional climate. The relation between group functioning and structural group characteristics was also examined. Mean age and group continuity (i.e., how long the children have already been attending the group) predicted group functioning, with higher group functioning in groups with older children and in groups with greater continuity. Group size and group constancy (i.e., how many days a week children attend the child care group together) did not independently contribute to the prediction of the group functioning variables.