Does Ontario's Dog Owners' Liability Act impose strict liability on dog owners?

Yes. The Dog Owners' Liability Act imposes a form of strict liability on dog owners for injuries their dog causes by biting or attacking a person, or another domestic animal, meaning the injured party generally does not have to prove the owner was negligent in how they supervised, trained, or contained the dog. This is a meaningful departure from ordinary negligence law, where proving the defendant fell below a reasonable standard of care is usually the central, most heavily contested part of a claim.

The Act reflects a specific policy choice that owners should bear responsibility for the risks their dogs pose to others, regardless of that particular dog's prior history or the precautions the owner had taken up to that point. This does not mean liability is automatic and unavoidable in every single case, however - the Act sets out specific circumstances, addressed in related questions about provocation and non-owner liability, where an owner's responsibility can be reduced or where a claim can genuinely be defended, so strict liability is the general rule but is not entirely without exception.