This article presents an analysis of 21 video-recorded family intervention sessions with children and parents in families where one or both parents are diagnosed with mental illness. The starting point for such family interventions is awareness of the risks that children run due to parental mental illness, e.g. development of mental health problems of their own. Previous studies have shown that openness about parents’ mental problems can reduce such risks. Family-intervention sessions are developed to assist children and their parents to talk about mental illness and related difficulties. Based on a dialogical and micro-sociological perspective, our objective is to analyse family-intervention sessions as professional practice and to illuminate various communicative means used by social workers to support children and parents in their talk about parents’ mental illness and its meaning for the children and the family. The analysis shows how professional practice is formed based on how the social workers solve communicative challenges in conversations with families about mental health problems: to create and maintain family support as a child-focused process; creating and maintaining family support as a child-focused process; spelling out parents’ mental problems; and confirming and normalizing.