In front of a crowd gathered at the bullring in the capital Bogota, renamed the Santamaria Cultural Square, Petro on Monday celebrated ending the "right to kill" animals for entertainment.
"Culture, and even less the justice (system), cannot say that it is culture to kill sentient beings, living creatures, for pleasure," said Petro, in reference to a 2018 Constitutional Court ruling permitting bullfights in places with such a tradition.
"If we have fun by killing an animal, we will have fun by killing human beings," Petro said, addressing the crowd which included animal rights activists.
Spectators chanted "No more 'ole'!", a slogan used during the legislative process by supporters of the law, which was passed by congress in late May.
Luana Delgado, an influencer and anti-bullfighting activist, underlined the importance of the ban being enacted at Bogota's bullring.
"A place where you saw blood, where you saw death, now you will see culture," she said.
The nationwide legislation paves the way for bullrings to be transformed into cultural spaces or sports venues.
Jesus Merchan, an animal rights campaigner, said to applause: "Today, we put an end to a long history of suffering."
The new law will be enforced from 2027, allowing time to convert arenas and provide alternative jobs to those who rely directly or indirectly on bullfighting.
Colombia joins other Latin American countries that have outlawed bullfighting, including Argentina, Brazil, Chile, Guatemala and Uruguay.
Bullfights are still held in Ecuador, Mexico, Peru and Venezuela, as well as in European nations France, Spain and Portugal.
