Aim The aim of the study was to investigate public health nurses’ interaction with families in the child health clinic setting where the mother is at risk of postnatal depression. Method Tape recorded interviews were conducted with 14 public health nurses working in different child health clinics in Finland. Findings The significant concepts that emerged from the data were the importance of discussion with the family, providing information and counselling, meeting the family, functionality of the relationship between the public health nurse and the family, and being professional. The relationships between these concepts take shape through preventing, identifying and treating postnatal depression. The core category to which all concepts are connected was identified as holistic co-operation with an individual family. Conclusion The public health nurse’s role in the child health clinic is to provide information and guidance, listen and answer families’ needs. Child health clinics are central places for families with newborns, and the work should be family-orientated. This could be achieved by inviting fathers to the clinic and discussing family issues, and asking concrete questions related to everyday life.