Consolidating Lawsuits in Ontario: When Courts Combine Related Cases

Sometimes two, three, or more lawsuits touch on the same underlying dispute — the same accident, the same failed project, the same chain of contracts — but end up filed as separate court files, sometimes even in different courthouses. Ontario courts have tools to bring related matters together, and understanding when a court will actually consolidate lawsuits can save everyone significant time and expense.

This guide explains what consolidation means, when courts are willing to order it, and what to weigh before asking for it.

What Consolidation Means

"Consolidation" and related orders — like directing that two or more actions be tried together, or that evidence in one be used in another — aren't always exactly the same thing, but they share a common goal: avoiding the waste, expense, and risk of inconsistent results that come from litigating overlapping disputes separately. Depending on the order sought, related actions might be:

• Formally consolidated into a single proceeding, or
• Heard together — tried at the same time, with the same judge, while technically remaining separate files — which achieves much of the same efficiency without merging the cases entirely.

When Courts Will Order It

Courts generally look for a meaningful overlap between the cases before ordering them combined. Relevant factors typically include:

• Whether the actions involve common questions of law or fact that would otherwise be litigated twice
• Whether combining the cases would save time and expense for the parties and the court, compared with running them separately
• Whether there's a real risk of inconsistent findings if the same underlying facts were decided by two different judges, or juries, in separate proceedings
• Whether combining the cases would cause unfair prejudice to any party — for example, by dragging an unrelated party into a much larger, more complex case than the one they're actually involved in

The court balances efficiency against fairness. Consolidation that saves time but genuinely disadvantages one of the parties is less likely to be ordered.

Factors the Court Weighs

• [ ] Do the cases share common facts, parties, or legal issues?
• [ ] Would separate trials risk contradictory findings on the same events?
• [ ] Are the cases at a similar procedural stage, or would combining them delay one significantly?
• [ ] Would any party be unfairly prejudiced by being drawn into a larger, more complicated proceeding?
• [ ] Is there a genuine efficiency gain, or would combining the cases just create confusion?

How to Ask for Consolidation

1. Identify the related file(s) — confirm the other action's court file number and current status.
2. Assess the overlap honestly. Consolidation motions are more likely to succeed when the overlap in facts or issues is genuine, not superficial.
3. Bring a motion asking the court to consolidate the actions, or to order that they be tried together, supported by evidence showing the overlap and the efficiency gained.
4. Address prejudice concerns proactively. If any party might be disadvantaged by combining the cases, anticipate that argument and respond to it in the motion.
5. Coordinate with the other parties where possible. A consolidation request is generally easier to obtain when it isn't strongly opposed.

Downsides to Consider

Consolidation isn't always the right move, even when the facts overlap:

• A stronger case can sometimes be weakened by association with a weaker one, or vice versa.
• Combining cases can complicate scheduling if the parties or their counsel have different availability.
• Where the parties' interests genuinely diverge despite overlapping facts, consolidation can create tactical complications that wouldn't exist in separate proceedings.

Frequently asked questions