It was also the opening goal of the 2014 tournament, briefly puncturing the carnival atmosphere across a country where expectations are sky high that the hosts will lift the trophy at the final in Rio De Janeiro on July 13.
The unfortunate Brazilian appeared to swing his right foot to clear the ball, but the late deflection saw it spin off his toe and roll tamely into the net.
The 26-year-old left back looked in mild shock as he stood in the goalmouth contemplating his blunder.
Marcelo later said he worked hard to remain calm.
"I thought, if I get down about it then I could damage the team," he said.
Goalkeeper Julio Cesar showed there were no ill feelings, patting his team-mate on the head, but for the next 18 minutes, Marcelo, and Brazil, looked on nervously as the hosts pressed for an equaliser.
"The fans helped me after I scored the own goal, they chanted my name and my team mates supported me and so I forgot about it and I got into the game again," added Marcelo.
"We didn't think about the (own) goal, but rather about scoring an equaliser and that's what happened."
As the match was being played, Brazilians took to social media sites to poke fun at Marcelo.
One photograph circulating showed him with a snide grin, with the caption: "Dilma, I dedicate that one to you" - a reference to Brazil's President Dilma Rousseff, whose popularity has tumbled in recent months.
Another picture of Marcelo carried the caption: "I still scored the first goal of the World Cup!" In the end, Marcelo's blushes were spared, his historic mistake laughed off, and the Sao Paulo skyline filled with fireworks.
— Kirk Gimenez (@KirkGimenez) June 12, 2014
- Sports & Recreation