Partial results from the Peruvian presidential elections show the World Bank economist Pedro Pablo is ahead of Keiko Fujimori with a narrow lead.
Latest results show Kuczynski had 50.32 percent support while Fujimori trailed on with 49.68 percent. The final results are expected later on Monday.
Keiko Fujimori is the daughter of the former authoritarian leader Alberto Fujimori, who was imprisoned for corruption and human rights abuses.
Fujimori had run a successful campaign but started to lose support in its last days due to fresh scandals involving her close advisers, and her father’s legacy.
Kuczynski, a 77-year-old former prime minister, investor and World Bank economist, portrayed himself as an honest and experienced leader.
He says he will end corruption, and revive economic growth that has slowed on weaker prices for Peru's mineral exports.
He also says his government will provide piped water to every Peruvian town.
Despite endorsing Fujimori during her first presidential bid in 2011, Kuczynski swept up the support of her critics from across the political spectrum and stepped up attacks against her in the final days of campaigning.
"We want a democratic country, a country committed to dialogue!" a jubilant Kuczynski said as he waved to supporters from a balcony at his campaign headquarters on Sunday evening before the partial count was announced.
While both candidates are fiscal conservatives who would maintain a free-market model in the resource-rich Andean economy, their styles and approaches differ widely.
The campaign pitted the Fujimori family's brand of right-wing populism against Kuczynski's elite background and stiff technocratic style.