This article describes the treatment framework and core therapeutic principles of the integrative brief systemic intervention (IBSI), a manualized six-session intervention intended for parents seeking couple therapy. IBSI aims to work on the couple's presenting problem, considering its specific impact in the marital and coparenting domains. The basic premise of IBSI is to consider that, when working with couples who have children, therapeutic work on their coparenting alliance may be used as a lever, as both parents may be particularly motivated to improve their relationship for their children's benefit. Increasing the coparenting alliance may then facilitate work on deeper conflicts within the marital relationship. The core therapeutic principles of IBSI are: (1) joining with the couple as romantic partners and a coparenting team from the start of the therapeutic process; (2) supporting the parents in increasing their awareness regarding their children's behavior and emotional experiences when facing their parents' conflicts; and (3) working on the spill- and cross-over effects between marital and coparenting relationships (i.e., exploring how conflict or positivity spills over from one relationship to the other or crosses over from one partner to the other). Therapeutic work following these main therapeutic principles is expected to improve the quality of both relationships. A clinical case is provided to illustrate the core therapeutic principles of IBSI.