Major corruption scandals involving state nuclear power agencies in recent years and a series of earthquakes last year further fanned public distrust and concerns over the safety of the plants.
He also vowed to introduce "post-coal" policy in line with his campaign promise to abandon coal power to ease air pollution in the country, which has the highest level of small air-pollutant particles among OECD member nations.
"We will abolish our nuclear-centred energy policy and move towards a nuclear-free era", Mr Moon said at a ceremony to mark the shutdown of the country's first and oldest nuclear reactor, known as Kori-1, near the city of Pusan.
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 announcement could have worldwide 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.
South Korean nuclear technology is now an export business headed by the Korea Hydro & Nuclear Power Company, a subsidiary of the Korea Electric Power Corporation (Kepco), which is 51 percent owned by the South Korean government.
Ex-UFC fighter in critical condition after boxing match
He was then immediately rushed to a nearby hospital and required emergency surgery to relieve pressure from a brain bleed. Family members told CTV Edmonton Tim Hague died Sunday after sustaining a brain injury in a boxing match Friday night.
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.
Moon on Monday also vowed to cut South Korea's reliance on coal. He said the seismic resistance of the country's nuclear power plants - which had been reinforced since the March 2011 Fukushima Daiichi accident in Japan - would be re-examined. He said the government will now "actively nurture safe and clean energy industries", including renewables and LNG power generation.
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.
The environment advocacy group Greenpeace beams a message reading "Goodbye Kori-1" on the wall of the nuclear reactor in Busan, some 450 kilometers southeast of Seoul on June 19, 2017. The Gyeongju natural disaster that struck South Korea in September 2016, which he acknowledged caused no deaths, has shown that Korea "is no longer a safe quake zone".
Even the decommissioning and "immediate dismantlement" of Kori-1 is to take place across a time span of 15 years, according to Segye Ilbo.