He acknowledged the defeat in a runoff race on Sunday, after early official results signalled a victory for the centre-left.
The centre-right government's candidate, told his supporters at his campaign headquarters that "with sadness, but without guilt, we can congratulate the winner", referring to Orsi.
"It is one thing to lose the elections and another to be defeated. We are not defeated," Delgado said on Sunday.
"Today, we can congratulate the one who won, the one who had the preference and do it with sincerity."
Alvaro Delgado has conceded defeat in the presidential election. (AP PHOTO)
Delgado's concession, with more than 57 per cent of official votes counted, ushers in Orsi of the centre-left Broad Front as Uruguay's new leader.
It spells an end to the short stint of the right-leaning government in Uruguay that, in 2020, with the election of President Luis Lacalle Pou, had broken 15 years of rule by the Broad Front.
The Broad Front drew international acclaim over those years for overseeing the legalisation of abortion, same-sex marriage and the sale of marijuana.
Yamandu Orsi will be Uruguay's next president. (AP PHOTO)
"I called Yamandú Orsi to congratulate him as President-elect of our country," current President Lacalle Pou wrote on social media platform X, adding that he would "put myself at his service and begin the transition as soon as I deem it appropriate".
Llamé a — Luis Lacalle Pou (@LuisLacallePou) @OrsiYamandu para felicitarlo como Presidente electo de nuestro país y para ponerme a las órdenes y empezar la transición apenas lo entienda pertinente.November 25, 2024
The win for Orsi makes the small South American nation the latest country to rebuke an incumbent party in this landmark election year where voters frustrated with post-pandemic economic malaise have punished ruling parties around the world, from the United States and Britain to South Korea and Japan.
But unlike elsewhere in the world, Orsi is a moderate who plans no radical changes and agrees with his opponent on key issues like combating childhood poverty and cracking down on organised crime.
Despite his promise to lead a "new left" in Uruguay, his platform resembles the mix of market-friendly policies and welfare programs that characterised the Broad Front's 15-year rule before the 2019 election brought centre-right President Luis Lacalle Pou to office.
He proposes tax incentives to lure investment and social security reforms that would lower the retirement age but fall short of a radical overhaul sought by Uruguay's unions that failed to pass in October, with Uruguayans rejecting generous pensions in favour of fiscal constraint.
with AP