Yes. You can sell a house with power of attorney in Ontario, provided the document is a continuing power of attorney for property, it was validly made, and it is registered at the land registry office before the transfer of title is registered. The person acting under it signs the listing paperwork and the closing documents in the owner's place.
Ontario has two versions. A continuing power of attorney for property keeps working after the grantor loses mental capacity. An ordinary one does not, and it stops at the exact point most families discover they need it. The rules come from the Substitute Decisions Act, which requires the document to be signed while the grantor was still capable and witnessed by two people. The attorney, the attorney's spouse, the grantor's spouse or child, and anyone under 18 cannot serve as a witness.
Ontario land transfers are registered electronically, and an instrument signed under a power of attorney will not be accepted unless that power of attorney has already been registered in the same land registry office. Your lawyer handles the registration using the original document or a notarial copy. Buyers' lawyers tend to ask about it early, so this is worth sorting out before the property is listed rather than in the week before closing. A real estate lawyer will also want to confirm the document has not been revoked.
Acting under a power of attorney makes someone a fiduciary. Decisions have to be honest, diligent, and made in the grantor's interest, which rules out selling the home to yourself, to your spouse, or at a friendly discount to someone you know. Ontario courts treat that kind of conflict seriously. There is a second restriction that catches people off guard: if the property is a matrimonial home, the Family Law Act still requires the other spouse to consent to the sale, and a power of attorney does not erase that.
The authority also has a hard endpoint. A power of attorney dies with the grantor. If the owner passes away before closing, the attorney no longer has any power to sign, and responsibility shifts to the estate trustee, which usually means waiting on probate. That is a different process with its own timeline, covered in selling a house after someone dies.
Related reading: How Do You Sell a House After Someone Dies in Ontario?, What Documents Do You Need to Sell a House in Ontario?, and What Does a Real Estate Lawyer Do in Ontario?