The Electoral Commission of the Asian country declared him the winner after obtaining 52.25 percent of the votes. By surpassing the fifty percent margin, Rajapaksa has secured his victory in the first round.
"I would like to inform everyone that I will execute everything you trusted me to do," said Rajapaksa in the announcement of the results, accompanied by his brother Mahinda, a two-period former president.
"Especially, at this moment, I happily say that I will fulfill everything that I have promised during my term in office."
Rajapaksa, a former defense secretary during Mahinda's 10 years in power, based his campaign for Saturday's elections on providing strong leadership on national security issues as the country reels from the coordinated Easter Sunday bombings that killed 269 people.
As Easter Mass on April 21 was celebrated a series of coordinated attacks targeted churches and luxury hotels in Sri Lanka leaving more than 250 dead and 400 injured.
Pope Francis said at the moment that it was one of the most devastating attacks in the history of Asia, one that tinged with pain and mourning such a significant celebration for the Christian community.
After the attacks, there has been a high level of insecurity regarding internal safety in the Asian country, a situation that Rajapaksa has promised to eradicate.
Following that line, his campaign was also backed by Sinhalese Buddhist monks, who have called for greater controls on the island's Muslim population after the attacks. Rajapaksa that "as we begin a new journey for Sri Lanka, we must remember that all Sri Lankans are part of this journey".
"Let us rejoice peacefully with dignity and discipline as we campaigned," the president-elect tweeted.
Rajapaksa will be sworn in as president on Monday at a ceremony in the central city of Anuradhapura, a former Sinhalese Buddhist heritage site about 160 km north of Colombo.