Collaboration between a psychotherapist and a patient occurs at the intersection of the therapeutic relationship and treatment method. Many methods contribute to collaboration, which is then experienced as a respectful, mutual, cooperative relationship. Despite its noble history and its empirical evidence as an important attribute in psychotherapy, collaboration has rarely been operationalized and illustrated in ways that might concretely guide clinical practice. This article introduces an issue of the Journal of Clinical Psychology: In Session designed to describe and illustrate the role of the psychotherapist in facilitating collaboration. Expert practitioners present case examples of collaboration in psychodynamic psychotherapy, cognitive-behavioral therapy, experiential therapy, family therapy, mindfulness-based cognitive therapy, multicultural therapy, and in the context of pharmacotherapy. In the final article, a practitioner-friendly review of empirical research on collaboration is offered.