No. Ontario has no law requiring a seller to disclose a death in a house, whether the death was natural, accidental, a suicide, or a homicide. Regulators treat a past death as a stigma rather than a physical defect, and stigmas fall outside the disclosure obligations that apply to Ontario home sellers.
The starting point is caveat emptor, the principle that puts the burden of investigating a property on the buyer. Ontario courts recognize one significant exception. A seller must reveal a material latent defect, meaning a hidden physical problem that makes a home dangerous, uninhabitable, or unfit to live in. A death does not change the physical condition of a property. That is why it lands on the stigma side of the line, alongside things like a rumoured haunting or a crime that happened nearby.
Having no duty to volunteer information is not the same as being free to lie. A seller who is asked directly whether someone died in the home and answers falsely opens the door to a misrepresentation claim. Real estate agents carry heavier obligations than their clients do. Under the Trust in Real Estate Services Act, the legislation that has governed Ontario agents since December 2023, registrants must treat everyone in a transaction with fairness, honesty, and integrity. The Real Estate Council of Ontario also expects a buyer's agent who knows about a stigma their client would consider important to pass that information along.
Because nobody is required to raise the subject, buyers who care need to ask. Put the question to the listing agent in writing and keep the answer. Searching the address online takes seconds and often turns up news coverage of any serious incident. Neighbours usually know a property's history better than any listing description will. It is also worth knowing that the rules change at provincial borders. Quebec requires sellers to disclose certain deaths, and some American states run their own disclosure regimes. Ontario leaves it to the buyer to investigate, which is exactly what a careful buyer should do before signing anything.
Related reading: Seller Disclosure Obligations in Ontario Real Estate, What Does Caveat Emptor Mean When Buying a Home in Ontario?, and What Is a Material Fact in Ontario Real Estate?.