Consolidation of lawsuits may be ordered by a court when two or more lawsuits involving the same or similar parties (plaintiff and defendant), legal issues, and factual issues are pending in the same court or in different courts in the same jurisdiction (state court system or federal court system). If the lawsuits are pending in different courts one case may be transferred to the other court, and the cases consolidated there.

Laws and rules regarding the consolidation—or transfer and consolidation—of lawsuits vary from state to state and in the federal court system.

In California, consolidation of lawsuits is governed by the California Code of Civil Procedure. Specifically, Section 1048 of the Code allows a court to order consolidation when two or more cases involve common questions of law or fact to avoid unnecessary costs or delay. The decision to consolidate is at the discretion of the court and is typically considered when the cases are so similar that consolidation would promote judicial efficiency and fairness to the parties involved. This can occur when the lawsuits are pending in the same court or when they are in different courts within the state court system. If the cases are in different courts, one may be transferred to the other for consolidation purposes. Additionally, the federal court system has its own rules for consolidation under Rule 42 of the Federal Rules of Civil Procedure, which similarly allows for consolidation when actions involve common questions of law or fact. The goal in both state and federal systems is to streamline the litigation process and reduce the risk of inconsistent judgments.