What counts as a marriage breakdown for the purpose of divorce in Ontario?

Under the federal Divorce Act, which applies throughout Canada including Ontario, a divorce can only be granted on the basis of marriage breakdown. The Divorce Act defines marriage breakdown in one of three ways: the spouses have lived separate and apart for at least one year; one spouse has committed adultery; or one spouse has treated the other with physical or mental cruelty.

The vast majority of divorces in Ontario are granted on the first ground — one year of separation — because it is the simplest and least contentious to prove. You do not need to assign blame or prove any wrongdoing. Adultery and cruelty are rarely used because proving them requires evidence and legal argument, making the process more expensive and adversarial than waiting for the year to pass.

It is important to understand that Ontario family courts do not consider fault or the reasons for the marriage breakdown when dividing property or determining support. Infidelity, for example, does not generally affect how property is split or whether spousal support is owed. The financial outcomes are based on economic principles, not moral fault.

If you are unsure whether your circumstances meet the legal definition of marriage breakdown or which ground to rely on, a family lawyer can advise you.