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 Washington State, consolidation of lawsuits is governed by the Washington State Court Rules, specifically CR 42(a), which allows for consolidation when actions involving a common question of law or fact are pending before the court. The court may order a joint hearing or trial of any or all the matters in question in the actions, consolidate the actions, or issue any other orders to avoid unnecessary costs or delay. The decision to consolidate is at the discretion of the court and is typically done to promote efficiency and to avoid inconsistent judgments. If the lawsuits are in different courts, a transfer may be necessary before consolidation can occur. The transfer process would be subject to the rules and statutes governing venue and jurisdiction. At the federal level, Rule 42(a) of the Federal Rules of Civil Procedure provides similar provisions for the consolidation of lawsuits that share common issues of law or fact, and federal courts have the discretion to transfer cases between districts for consolidation under 28 U.S.C. § 1404(a) if it is in the interest of justice and more convenient for the parties and witnesses.