Can a toxic or hostile work environment amount to constructive dismissal in Ontario?

Yes. A genuinely toxic or hostile work environment can amount to constructive dismissal if the conduct is serious enough that it breaches the employer's fundamental obligation to provide a reasonably tolerable workplace, effectively making continued employment untenable for a reasonable person in that position. This is a high bar, and ordinary workplace friction, a difficult manager, or an isolated unpleasant incident generally will not be enough on their own to meet it.

Courts look at the pattern and severity of the conduct over time, whether the employer knew about it and failed to reasonably address it once raised, and whether a reasonable employee in the same position would feel they had no real choice but to leave. Because these claims often turn on a course of conduct rather than one clear event, documentation becomes especially important - emails, incident reports, and any complaints made to the employer along the way - both to show the pattern genuinely existed and to show the employer had a real opportunity to fix the problem and failed to do so.