Left-leaning businessman defeats retired general in election marked by voter apathy.
A day after winning the run-off, Colom urged all Guatemalans to unite behind his plans to reduce poverty and end ethnic divisions.
“We will work to attain a national brotherhood with our 23 indigenous groups,” he said on Monday. “This will be a great opportunity to unify the country.”
Colom, of the centre-left National Unity of Hope party and an ordained Mayan minister, said he would ask the Mayan Elders National Council, a group of spiritual leaders, for guidance.
In a concession speech on Sunday night, Molina, who ran on a tough anti-crime platform, pledged to be “a constructive opposition” and work together with the new government to fight crime.
“We’re willing to keep fighting the war against impunity, the war against corruption and against violence”
Otto Perez Molina, losing candidate
“We’re willing to keep fighting the war against impunity, the war against corruption and against violence,” he said.
Guatemala has one of the highest murder rates in the world and about 6,000 people were murdered in the country last year.
About 50 candidates and supporters were killed before the first round of voting, and a further five political murders were reported since then.
The country has been plagued by violence for much of its recent history.
The army ruled the Central American country for decades until the mid-1980s and committed hundreds of killings.
As many as 200,000 people are thought to have been killed during 36 years of civil war before the government and left-wing rebels made peace in 1996.
The country is a major transit point for cocaine shipped to the US, and drug cartels have grown in influence in recent years.