High-conflict separating and divorcing couples often struggle with unconscious conflicts that are projected onto arguments about the children resulting in interminable disputes. Approaches that primarily emphasise parenting and communication skills, without a more in-depth focus, are insufficient to address these complicated dynamics. In contrast, I offer a model of psychoanalytic co-parent therapy that enables the promotion of containment, reduces splitting, destructive aggression, and defensive projection, helps the partners become more psychologically separate, and allows access to feelings of loss. A key component of this model is the development of the parenting plan, a shared agreement about coparenting the children that functions on both a conscious and unconscious level. The therapist works with high-conflict couples to create the parenting plan, whilst at the same time addressing the underlying psychological vulnerabilities. The parenting plan may serve as a type of transitional object for the couple, facilitating their psychological development, and aiding in their transition from a separating or divorcing couple to a co-parent couple. This process can be internalised, communicated to the children, create less conflict, mitigate the enduring impact of the loss, and benefit the entire family.