The 25-year-old was officially granted Spanish nationality on Oct. 3, and will now represent Spain should he receive a call up.
He says he is wary of the issues it may cause in his homeland, but that it is not a problem with him.
"I do not want to create problems with anyone in Brazil," Costa told Marca. "I want people to accept my decision. Would I have a problem scoring for Spain against Brazil in the World Cup Final? No."
On the topic of a potential call up for la Roja, Costa says he is far from promised a place in the squad, despite his excellent form for Atletico so far this season.
"Vicente del Bosque has promised me nothing," he continued. "I know I will have to work very hard to earn a call up, and hopefully my current form will ensure that."
Finally, the controversial striker admits he doesn't always behave, but puts it down to a tough upbringing in Brazil.
"I have come from having nothing to having everything I want," he said. "I know what I do on the pitch isn't always right, but I am also provoked more than a lot of players. I came to Spain at a young age, with no friends or family and in a very different culture. It has not been easy."
Costa has scored 10 goals in just eight league games for Diego Simeone's side so far this season.