The province's Community Safety Ministry and its Information and Privacy Commissioner have been locked in a lengthy battle over the data, which the government says could identify individual offenders.
Earlier this year, Ontario's top court ruled the information should be released.
The privacy commissioner had previously ordered the records be disclosed to an unnamed journalist, who made the request under Freedom of Information laws.
Last year, the Divisional Court dismissed the ministry's application for a judicial review of the commissioner's decision.
The ministry had said the information could reasonably lead to an expectation of harm, facilitate the commission of an illegal act or hamper the control of crime.
However, in ordering release of the data in 2009, the privacy commissioner found the ministry's concerns baseless.
The ministry provided no evidence that providing the first three digits of the postal codes could be used to locate convicted sex offenders within communities, the appellate court ruled.
Sex offenders are required by law to notify the Ontario registry if they change addresses. Information in the registry is normally off-limits to anyone other than police involved in an investigation.
The ministry worried that disclosure of the information could prompt offenders to go underground out of fear of vigilantism.
On average, more than 24,000 people live in the "forward sortation area" identified by the first three digits of a postal code.