The delay was caused by security fears over Google Maps, according to Reuters.
In South Korea, functions on Google Maps are limited by the government for national security reasons.
The makers did not specify how they had worked around the problem but some reports suggested that they had to use publicly available data to fill gaps.
The game, which was jointly developed by Nintendo and Niantic Labs, challenges users to walk around the real world capturing virtual monsters and training them to fight each other.
It proved a big hit when it was released in July and, since then, it has been downloaded an estimated 500 million times.
But the game has declined rapidly in downloads in recent months, according to app measuring firm App Annie.
US downloads fell from more than 80 million in the US in July 2016 to 1.5 million in November, it suggested.
South Korea is the one of the world's biggest gaming markets alongside China, Japan and the US.
According to analyst firm IHS, South Koreans spend more per capita on mobile games than any other country other than Japan.
Gaming analyst Jack Kent said: "South Korea is one of the world's most lucrative mobile games markets, so should be a big boost for the game.
"The delay in launching highlights some of the complexities involved in operating a location-based title that relies on partners to provide the underlying infrastructure."