- This study examines whether the strength of the parent-therapist alliance, measured during the task of alliance building with parents alone, predicted the extent of parents’ attachment-promoting behaviour in the subsequent conjoint parent-adolescent attachment task in the context of attachment-based family therapy (ABFT). Nineteen suicidal and depressed adolescents and their parents received 12 weeks of ABFT. The parent-therapist alliance and parents’ attachment-promoting behaviour were each measured observationally by two separate and independent groups of raters. The findings show that the strength of the parent-therapist alliance predicted parents’ subsequent attachment-promoting behaviour. However, parents’ attachment-promoting behaviour did not predict the post-treatment outcomes. Clinical and methodological implications are discussed. Practitioner Points Good parent-therapist alliances are linked to parents being empathic, curious and non-defensive during emotional conversations with their suicidal and depressed adolescents. Parental attachment-promoting behaviour, including attunement, empathy, and active listening, may not always be sufficient curative factors. Once the parent-adolescent attachment relationship improves, parents may support their adolescent as they cope with school and peer conflict.