The ex-NBA man said he flew straight to Italy when he heard there was a chance a black man could be picked as the next pontiff.
"You know he's going to be the first black pope so basically hey I'm here to support," he said.
Ghanaian Cardinal Peter Turkson has been named a possible contender for the position of pope.
"They're trying to elect a new pope and surprisingly enough he's a favourite and he's black. That's what I mean, just to support that. I don't want to people to get it all twisted where it's like just because Obama's black, this guy has to be black. I think the guy that's going to be successor of the last pope, he should be more of an improvement instead of a hindrance," he added.
But Rodman said the most important thing was that cardinals sequestered inside the Sistine Chapel picked the right man for the job.
Sporting a garish flowery jacket over a white T-shirt, Rodman was surrounded by onlookers and reporters braving the rain outside the Sistine Chapel where 115 cardinals were choosing a successor to Pope Benedict.
Rodman played on five NBA championship teams during his basketball career, which ran from 1986 to 2000. He played for five teams and in his peak years he was the league's top rebounder and one of its best defenders. He was chosen for the Basketball Hall of Fame in 2011.
Rodman's basketball skills were matched by his flamboyance - party lifestyle, multi-coloured hair, blankets of tattoos, piercings in his ears, nose, lips and eyebrows and showing up in a wedding gown, complete with veil, to promote his autobiography.