As a result, operator Newmont Mining's (NYSE: NEM) and Compania de Minas Buenaventura SAA's stakes revert to 51.35% and 43.65% respectively.
Sumitomo essentially takes the place of previous 5% holder International Finance Corporation, whose stake was repurchased by Minera Yanacocha in December.
Sumitomo partners with Buenaventura at the Cerro Verde mine in Peru and previously had a partnership with Newmont at Batu Hijau in Indonesia.
"Sumitomo brings mining expertise, high performance standards, and a shared commitment to extending profitable and responsible production at Yanacocha," Newmont executive vice president of strategic development Randy Engel said.
Buenaventura CEO Victor Gobitz echoed the sentiment, adding the trio shared a commitment to safe, profitable and responsible production extension through the Quecher Main and Yanacocha sulphides projects.
Sumitomo said it would also join in contributing to the sustainable economic development of local communities.
Yanacocha's Quecher Main project was approved in October and is expected to extend the mine's oxide life to 2027 and "serve as a bridge to future growth options" including the sulphide deposits.
Yanacocha is expected to produce 470,000-545,000 ounces of gold this year on a 100% basis, according to Newmont's March quarterly.
The Quecher Main capex is $250-$300 million and is set to extend the mine's production with an average annual 200,000oz between 2020-2025 at an all-in sustaining cost of $900-$1,000/oz.