Does filing an appeal automatically stop the other side from enforcing the judgment in Ontario?

Often, yes, but not universally, so it's worth confirming rather than assuming. Launching an appeal to the Court of Appeal for Ontario generally puts an automatic hold, or stay, on enforcement of the specific order being appealed, meaning the winning party generally can't proceed with a writ of seizure and sale, garnishment, or similar enforcement steps while the appeal is pending. This exists to avoid the unfairness of a judgment being fully enforced, potentially causing irreversible harm, only for the appeal to later succeed and leave the appellant trying to undo damage that's already been done.

This automatic stay isn't universal, however; certain kinds of orders, including some injunctions and support-related orders, generally aren't automatically stayed just because an appeal has been filed, reflecting a judgment that ongoing harm from not enforcing those orders can outweigh the appellant's interest in a pause. Even where an automatic stay would otherwise apply, a court can be asked to lift it in appropriate circumstances, and conversely, a party without an automatic stay can ask a court to impose one. Because the rules differ depending on the type of order and appeal route involved, confirming the specific stay position for your situation is an important step immediately after filing an appeal.