It also continued a trend in recent years that has seen many countries in the region swing to the left, although some would argue those are populist moves as much as ideological ones.
Argentina, Peru, Chile, Mexico, Bolivia and Honduras have all moved to the left in their last elections and Petro's victory sparked a feeling of fraternity amongst these leaders.
"Your victory validates democracy and ensures the path towards an integrated Latin America in this time when we demand maximum solidarity amongst brother peoples," said Argentina President Alberto Fernandez on Twitter.
Chile President Gabriel Boric, who was elected earlier this year to replace conservative Sebastian Pinera, said Petro's victory was a "joy for Latin America."
"We will work together for the unity of our continent in the challenges of a world changing rapidly," he tweeted.
Peru's Pedro Castillo, a rural school teacher and trade unionist, said he looked forward to working with an ally, something that has been in short supply in his homeland where the right-wing opposition dominates congress.
"We are united by a common feeling that seeks improved collective, social and regional integration for our peoples," he said.
"Latin American integration is strengthened," added Bolivia's Luis Arce.
Mexico President Andres Manuel Lopez Obrador said Petro's success could heal the wounds in a country in which political assassinations are not uncommon.
He referenced the 10-year Colombian civil war that broke out following the 1948 assassination of leftist presidential candidate Jorge Eliecer Gaitan and was the precursor to the six-decade long conflict between the state and left-wing guerrillas.
"Today's triumph can be the end of this curse and the awakening for this brotherly and dignified people," said Lopez Obrador.
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