A serious question to be tried is the first part of the usual test for a conventional interlocutory injunction. It is generally a relatively low threshold. The court is not conducting the full trial on the injunction motion; it is making a preliminary assessment to determine whether the claim is not frivolous or vexatious and whether there is a genuine issue that should be preserved until the merits can be decided.
The concept comes from the injunction framework in RJR—MacDonald Inc. v. Canada (Attorney General). At this stage, the moving party does not normally have to prove that it will ultimately win the lawsuit. Instead, there must be a real legal or factual dispute capable of adjudication.
For the complete three-part framework, see What do you have to prove to get an interlocutory injunction in Ontario?.
What does the court look at at this stage?
The Ontario Superior Court of Justice may review the pleadings, affidavit evidence, contractual documents, correspondence, and other materials filed on the motion to determine whether the claim raises a genuine issue.
The court is generally not deciding credibility disputes or making final findings of fact at this preliminary stage. Those issues may ultimately require fuller evidence, cross-examinations, discovery, or trial.
The purpose of this first stage is therefore screening rather than final adjudication.
Does meeting this threshold mean the injunction will be granted?
No. Showing a serious question to be tried is only the first step.
The moving party must also address irreparable harm and the balance of convenience. A case can therefore raise a genuine legal issue and still fail to justify interlocutory relief.
This distinction is important because an injunction is an exceptional remedy. The existence of a legitimate lawsuit does not automatically establish that the court should intervene before the underlying dispute has been finally determined.
For the broader role of the remedy, see What is an injunction in Ontario?.
Is the threshold always this low?
No. The applicable first-stage threshold depends on the nature of the interlocutory order being requested.
Where the requested order is mandatory in substance—meaning that it requires the responding party to take positive action rather than simply restraining conduct—the moving party generally faces a more demanding standard.
In R. v. Canadian Broadcasting Corp., 2018 SCC 5, the Supreme Court of Canada held that an applicant seeking a mandatory interlocutory injunction must establish a strong prima facie case, rather than merely a serious question to be tried. This requires a strong likelihood, based on the law and the evidence presented, that the applicant will ultimately succeed at trial. The applicant must still establish irreparable harm and show that the balance of convenience favours granting the injunction.
The substance of the requested order matters more than the label attached to it. If the practical effect of the order is to require a party to take positive steps, the court must consider whether the heightened mandatory-injunction standard applies.
See What is a mandatory injunction in Ontario? for the different test applicable to mandatory relief.
How does ME Law assess the first stage of an injunction motion?
ME Law assesses the legal basis of the underlying claim together with the pleadings, affidavit evidence, documentary record, urgency, potential harm, and practical effect of the proposed order.
An important part of that assessment is determining whether the requested relief is a conventional interlocutory injunction governed by the serious-question threshold or is mandatory in substance and therefore engages the higher strong prima facie case standard.
That distinction can materially affect both the evidence required and the way the injunction motion should be framed.
Contact ME Law if you need advice about seeking or responding to an interlocutory injunction in Ontario