Speaking at a press conference Thursday, Dunga confirmed the 22-year-old would replace injured defender Thiago Silva, who has captained Brazil since 2011, reports Xinhua.
"It has already been confirmed. It's going to be Neymar," said Dunga, who did not say whether the appointment was permanent.
"He is a reference for Brazilian football. He has quality and despite his age, he is experienced. He is an example for his teammates."
Brazil's clash against Colombia at Miami's Sun Life Stadium Friday night will be a replay of this year's World Cup quarter-final between the teams, which Brazil won 2-1.
It will be Dunga's first match in charge since replacing Luiz Felipe Scolari after Brazil failed to make the World Cup final as hosts and pre-tournament favorites.
The Selecao will also play Ecuador at Boston's MetLife Stadium Sep 9.
Dunga said Neymar had responded positively after being told of his new leadership role.
"He is a player who likes challenges and to win," said Dunga, who also coached Brazil from 2006 to 2010.
"When we broached the subject we spoke about the advantages and disadvantages. The position brings with it responsibility, but there are also other players in the squad who are leaders."