He also pledged to decommission 10 aged coal power plants within his five-year term and to stop building new coal power plants.
The announcement could have global significance as South Korea counts as one of the top producers of nuclear power in the world and had been looking to export it's technology and expertise - most recently to the United Kingdom. "So far, the country's energy policy focused on low prices and efficiency".
"We will abolish our nuclear-centred energy policy and move towards a nuclear-free era", Mr Moon reportedly said as he marked the closure of the reactor built in 1977. "We will completely scrap construction plans for new nuclear reactors that are now under way", Moon added.
South Korea is also one of the few countries that have exported its nuclear reactor technology, an area once seen by some of its construction companies as a new cash cow. Former President Lee Myung-bak promoted nuclear energy as part of the country's clean energy strategy and helped local companies win billions of dollars worth of deals to build nuclear reactors overseas. The plant was originally created to run for 30 years, but the government decided in December 2007 to extend its operation for another decade.
Moon said he will soon reach a consensus on the Shin Kori No.5 and Shin Kori No.6 reactors after fully considering their construction costs, safety and the potential costs of paying compensation.
The country's second-oldest reactor, Wolsong 1, will be shut down as soon as possible, he said, taking into consideration the power supply and demand situation.
South Korea has 25 nuclear reactors, supplying about a third of the country's total electricity. Its nuclear electricity production was the fifth-largest in the world, according to the World Nuclear Association.
The public's support for nuclear power has weakened since the 2011 Fukushima meltdown and a 2013 corruption scandal over fake safety certificates for reactor parts.
At the same time, the government plans to slash the use of coal, which generates around 40% of South Korea's energy but is a major cause of global warming.
Numerous reactors are located near residential areas along the country's southeast coast.
The former president Lee Myung-bak saw nuclear as an important source of clean energy, while Park wanted to increase the number of reactors to 36 by 2029.