A caucus is a private meeting between the mediator and one party during mediation, separate from any joint session. Caucuses allow a party to speak candidly with the mediator about their concerns, their bottom line, or information they are not ready to share directly with the other side.

Information shared in a caucus is held in confidence by the mediator unless the disclosing party authorizes the mediator to share it. The mediator uses caucus information to understand each party's actual interests and constraints.

Many mediations are conducted entirely in caucus format and the parties never sit together. This is particularly common in high-conflict cases and domestic violence cases.