The 49-year-old independent candidate Yoneyama, who has had the support of the Communist Party and two other small groups, won with 53.2 per cent of the vote against his rival Tamio Mori, the electoral commission of Niigata reported Monday.
Since the start of the campaign, Yoneyama expressed a clear position against restarting the Kashiwazaki-Kariwa nuclear plant, which was shut down after the Fukushima nuclear accident in 2011. His opponent Mori never took a clear position on the issue, EFE news reported.
"As I have promised all of you, under current circumstances where we can't protect your lives and your way of life, I declare clearly that I can't approve a restart," Yoneyama said after the results were out.
The victory of the anti-nuclear candidate comes after Hirohiko Izumida, the former governor who has always expressed a cautious view on the restart of the Kashiwazaki-Kariwa complex, announced this year that he would not seek re-election after serving three consecutive terms.
Many members of the ruling Liberal Democratic Party (LDP) have expressed concern over the possibility that Yoneyama will block the restart of Kashiwazaki-Kariwa plant, which has seven reactors capable of generating up to 8.2 million watts of electricity.
To boost the Japanese economy, which is highly dependent on external energy sources, the government aims to reopen plants in the country under new and stricter safety requirements, vowing to prevent a repeat of the situation produced by the 2011 tsunami.
The nuclear plant in Niigata is owned by Tokyo Electric Power Company (TEPCO), the company behind the Fukushima nuclear disaster, and suffered a small radioactive leak after a 6.6-degree earthquake that hit Niigata in 2007.