Drawing on decades of research in family systems, coparenting, and developmental science, we present a clinical approach to address unmet service needs in children's mental health. Specifically, we describe Lausanne Family Play -Brief Intervention (LFP-B) -a manualized family systems approach providing a caregiver-caregiver-child therapy (and sibling/s, when applicable). The LFP-B is ultra-brief, typically delivered in as few as three sessions (two assessment sessions followed by a video feedback session), with the aim of reducing children's mental health symptomatology by enhancing the coparenting relationship. We review literature on systemic family therapies and provide a rationale for including coparents and children in child mental health care. We then provide a rationale for using behavioral observations and video feedback in treatment, drawing on research in related family-based treatments (e.g., parent-child therapies). Finally, we provide an overview of the LFP-B manual and a case illustration.