Can You Add a New Defendant to a Lawsuit in Ontario?

Can you add a new defendant to an Ontario lawsuit after it has already started?

Yes — Ontario’s Rules of Civil Procedure make it relatively straightforward to amend a statement of claim to add a new party, provided the amendment is not an abuse of process and any prejudice to the other side can be addressed through a costs award. The recent decision in Eco Kids-Child Care Centre Inc. v. Emmabby Prop. Mngmt Inc., 2026 ONSC 4335 (CanLII), walks through exactly how that analysis works in practice.

What is the legal test for amending a statement of claim in Ontario?

The governing rule is Rule 26.01 of Ontario’s Rules of Civil Procedure, and the test strongly favours allowing amendments. Under the approach confirmed in Schembri v. Way, a court must grant leave to amend unless the opposing party can show either an abuse of process or prejudice that money cannot fix. That is a high bar for the party opposing the change.

On the motion, the court does not weigh competing evidence or decide who is right. Instead, it treats the proposed new allegations as true and capable of being proven at trial. The question is simply whether the amended claim discloses an arguable case — not whether it will ultimately succeed.

What counts as non-compensable prejudice when adding a defendant?

Non-compensable prejudice means harm that a costs award cannot undo. In most cases, the inconvenience and expense of responding to a new claim can be addressed by ordering the plaintiff to pay the new defendant’s costs thrown away. Courts have consistently held that this kind of litigation inconvenience does not justify refusing an amendment.

The prejudice that could justify refusal would be something more serious — for example, evidence that has been irretrievably lost because the new party had no reason to preserve it, or a situation where the amendment fundamentally changes the nature of the proceeding at a very late stage.

What happens to a limitation period defence when a new defendant is added?

This is often the most contested issue when a plaintiff seeks to add a party. Under sections 5 and 21(1) of Ontario’s Limitations Act, 2002, the two-year clock starts running when the plaintiff knew — or reasonably ought to have known — about the claim against the specific defendant being added. General knowledge that something went wrong is not enough.

The court applied the Supreme Court of Canada’s framework from Grant Thornton LLP v. New Brunswick, which confirms that discoverability is defendant-specific. In this case, the record did not contain enough information to resolve whether the plaintiff had discovered the supervising lawyer’s involvement more than two years before bringing the motion. Rather than refusing the amendment on an incomplete record, the court granted leave while expressly preserving the limitations defence for the defendant to raise later on a fuller evidentiary record.

Can a party get an adjournment partway through a motion hearing?

Generally, no — and this decision is a useful reminder of that. During the hearing, the responding party asked for an adjournment to file supplementary materials after the plaintiff had already completed its submissions. The court refused. Allowing one side to gather additional evidence after hearing the other side’s full argument would be procedurally unfair. If more time or materials were needed, the request had to be made at the outset of the hearing, not after the plaintiff had shown its hand.

This principle applies broadly: if you know you need more time or more evidence, raise it before the hearing begins, not during it.

How are costs decided after a motion like this?

The successful party on a motion is generally entitled to costs, but the scale matters. The plaintiff here sought costs on a substantial indemnity basis — a higher scale typically reserved for cases involving bad faith, reprehensible conduct, or offers to settle that were unreasonably rejected. The court declined to award substantial indemnity costs, following the approach in Net Connect Installation Inc. v. Mobile Zone Inc.

Instead, the court awarded partial indemnity costs, the default scale in Ontario civil litigation. The court noted that the opposition to the amendment was not without merit, and that proportionality required a costs award within the reasonable expectations of the parties. The practical takeaway: simply winning a motion does not automatically entitle you to the highest cost scale.

Practical takeaways for plaintiffs and defendants in Ontario civil litigation

• Act early if you want to add a party. While Rule 26.01 is permissive, adding defendants late in a proceeding increases the risk that a limitations defence will succeed — and the court will not always resolve that issue in your favour on a thin record.
• Gather your evidence on discoverability before the motion. The limitation period question is defendant-specific. You need to show when you first had reason to connect this particular person to the alleged wrongdoing.
• Raise procedural concerns at the start of a hearing. If you need more time or want to file additional materials, say so before the other side presents its case — not after.
• Do not assume you will get substantial indemnity costs just because you win. Courts apply that elevated scale sparingly. Budget your expectations around partial indemnity unless there is clear misconduct or a relevant offer to settle.
• Preserve your defences even when an amendment is granted. A court granting leave to amend does not decide the merits. Limitation period and other defences remain fully available after the amendment is allowed.

Our Ontario litigation lawyers regularly advise on pleadings amendments, limitation period issues, and civil motion strategy across the province. Whether you are trying to add a party to an existing claim or defending against one being added, getting the procedural steps right from the beginning is critical.

If your matter is in the Greater Toronto or Hamilton area, our teams serving Burlington and Mississauga can assist with Superior Court proceedings at any stage. UL Lawyers offers a free initial consultation from our Burlington office and works with clients across Ontario — reach out to learn how we can help with your civil litigation matter.

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This article is automated commentary on a public court decision and is for general information only — not legal advice. Decisions rely on facts unique to each case. If you are affected by a similar issue, contact a lawyer for advice specific to your situation.