Reinfeldt, concluding a four-day official trip to Brazil and Chile, spoke earlier Thursday at an energy seminar before meeting Pinera at the presidential palace.
Chile relies heavily on exports of its natural resources. Copper alone provides one-third of government revenue, according to US estimates. Lithium, iron, wood and fruits are among Chile's exports.
"A country that will invest $50 billion during this decade in mining has to make an effort because mining is sustainable," Pinera said.
Mining and forestry, he added, "are very important to both nations." The "green technologies" agreement focuses on urban development that protects the environment.
Earlier in the trip, Reinfeldt discussed ethanol production, environmental concerns and technological cooperation with Brazilian President Dilma Rousseff.
On Wednesday, Reinfeldt told Brazilian business leaders that there should be a global "green economy" with sustainable growth. He said it would be a huge challenge but "there is no alternative."