Do I need a court's permission before serving a lawsuit on someone outside Canada from Ontario?

It depends on the connection between your claim and Ontario. Ontario's civil procedure rules set out specific categories of claims considered closely enough connected to the province — such as a contract made or breached here, a wrong that happened here, or a dispute over property located in Ontario — where a plaintiff can generally serve a defendant outside Canada without first asking a judge for permission. Outside those recognized categories, a plaintiff generally needs to bring a motion for leave to serve outside Canada, explaining to the court why it's appropriate for an Ontario court to hear a case involving someone located abroad.

Getting this step wrong can have real consequences: serving without leave when it was actually required can leave that service open to challenge later, potentially unwinding steps taken based on it. Even where leave isn't strictly required, the practical mechanics of serving someone abroad still depend on the destination country's own rules, which sometimes require going through a formal treaty process rather than simply mailing documents. Before attempting service on a defendant outside Canada, it's worth confirming both whether leave is needed for your specific claim and what method of service is actually recognized in that country.