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 Massachusetts, the consolidation of lawsuits is governed by both state procedural rules and statutes. Under the Massachusetts Rules of Civil Procedure, specifically Rule 42(a), a court may order a joint hearing or trial of any or all the matters in issue in the actions; it may order all the actions consolidated; and it may make such orders concerning proceedings therein as may tend to avoid unnecessary costs or delay. This is applicable when there are common questions of law or fact to ensure efficiency and consistency in the judicial process. Additionally, the court has the discretion to transfer cases from one court to another within the state court system for the purpose of consolidation. In the federal court system, similar provisions exist under the Federal Rules of Civil Procedure, which allow for consolidation when actions involve a common question of law or fact. The decision to consolidate is at the discretion of the court and is intended to streamline the process, reduce litigation costs, and prevent inconsistent judgments.