Can I sue for psychological injury caused by witnessing an accident in Ontario?

Yes, in the right circumstances. Ontario law recognizes claims for genuine psychiatric injury caused by witnessing or learning about an accident, sometimes referred to as nervous shock, but the harm has to be a recognizable, diagnosable psychiatric condition - ordinary grief, distress, or upset on its own generally is not enough, however understandable that reaction might be. Courts also require that this kind of harm was reasonably foreseeable given the circumstances, meaning it should have been apparent that a person in your position could suffer real psychiatric injury from what happened.

Canadian courts have moved away from a rigid checklist of factors like exact physical proximity to the event or precisely how you learned about it, and instead apply a more general foreseeability-based approach, though those traditional factors - your relationship to the person directly injured, how immediately you experienced or learned of the event, and the severity of what happened - remain relevant context for assessing foreseeability. Because these claims turn heavily on medical evidence, a proper diagnosis from a qualified professional, along with a clear account of how the psychiatric injury developed after the event, is essential to a claim of this kind succeeding.