According to data from the 1997 NICHD Study of Child Care, center-based child care can have deleterious effects on children's social–emotional development. We hypothesized that training child care professionals to develop positive relationships with children in their care would improve the quality of center-based child care. Thirty-three professional caregiver–child pairs participated in the intervention group and 24 professional caregiver–child pairs were assigned to a care as usual comparison group. The intervention consisted of an informational and a practice component with an emotional availability (EA) coach. The infants and toddlers (ages 11 to 23 months) in the classrooms were enrolled in the project only if they spent at least 20 hr per week in center-based care. The measures included were (a) the EA Scales, (b) the Attachment Q-Sort, and (c) the Classroom Interaction Scale. The intervention group professional caregiver–child relationships showed improvements on the EA Scales, Attachment Q-Sort, and the Classroom Interaction Scale from pre- to posttest, compared to the comparison group, who showed some decrements over a comparable period of time.