Pinera, who governed the South American nation from 2010 to 2014, defeated leftist candidate Alejandro Guillier during a second round of voting Sunday.
Chile's Electoral Service said Pinera won with 54.58% of the votes. Guillier came in second with 45.42%, a much wider margin than originally predicted by pollsters.
Outgoing President Michelle Bachelet, a socialist leader who also served two presidential terms, had backed Guillier, who had pledged to continue many of her policies and programs.
However, Bachelet's approval ratings had plummeted in recent months as critics accused her of being out of touch with her constituents and of not managing the country's lagging economy, which was heavily affected by dropping copper prices.
Pinera, a businessman turned politician, is worth an estimated $2.7 billion, according to Forbes
. He founded the credit card company Banco in the 1970s and, during his previous stint as President, honored a promise to divest his assets, the magazine reports.
The election represents a return to the right in Chile and adds to the wave of conservatism sweeping through Latin America in countries like Argentina, Brazil and Paraguay -- and sees another billionaire leader take the reins in the Americas.
The presumptive leader addressed supporters in the capital, Santiago, following the announcement of the runoff results.
"We receive this triumph with humility and hope," Pinera said, according to CNN affiliate CNN Chile, while the crowd chanted "Chile has been saved!" and "Cecilia, Cecilia," referring to his wife, Cecilia Morel.
He said he'd seek the counsel of "those who have had the privilege and honor of being president in the past," he said, likely referring to Bachelet and their predecessor, Ricardo Lagos.
"I look forward to receiving your sound and valuable advice and I will present great proposals to my compatriots to face and resolve the problems affecting Chileans. ... We can think differently. Long live our differences! We should never allow the pluralism of ideas to turn us into enemies."
In the speech, delivered at a hotel in Santiago, he sounded a note of reconciliation for the country.
"I will govern for all Chileans," he said.