Background: Work with families and families at risk within the field of music therapy have been developing for the last decade. To diminish risk for unhealthy child development, families with emotionally neglected children need help to improve their emotional communication and develop healthy parent-child interactions. While some researchers have investigated the effect of music therapy on either the parent or the child, no study has investigated the effect of music therapy on the observed interaction between the parent and child within the field of child protection. Objective: The purpose of this study was to investigate the effect of a dyadic music therapy intervention on observed parent-child interaction (mutual attunement, nonverbal communication, emotional parental response), self-reported parenting stress, and self-reported parent-child relationship in families at risk and families with emotionally neglected children, ages 5-12 years. Method: This was a randomized controlled trial study conducted at a family care center in Denmark. Eighteen parent-child dyads were randomly assigned to receive 10 weekly music therapy sessions with a credentialed music therapist (n = 9) or treatment as usual (n = 9). Observational measures for parent-child interaction, self-reported measures for parenting stress and parent-child relationship were completed at baseline and 4 months post-baseline assessment. Results: Results of the study showed that dyads who received music therapy intervention significantly improved their nonverbal communication and mutual attunement. Similarly, parents who participated in dyadic music therapy reported themselves to be significantly less stressed by the mood of the child and to significantly improve their parent-child relationship in terms of being better at talking to and understanding their children than parents who did not receive music therapy. Both groups significantly improved in terms of increased positive and decreased negative emotional parental response, parenting stress and stress in general. There were no significant between group differences in self-perceived autonomy, attachment, and parental competence. Conclusions: The dyadic music therapy intervention examined in this study improved emotional communication between parent and child and interaction after 6 to 10 sessions and can be considered as a viable treatment alternative or supplement for families at risk and families with emotionally neglected children.