Luiz initially appeared to connect with Thiago Silva's flick-on from a corner to give the Selecao a one-goal lead on 18 minutes yesterday.
However, some replays suggested that Chile's Gonzalo Jara may have got the final touch, but the governing body has now definitively claimed that it will go down as Luiz's goal.
"The technical study group has looked at this and the goal will remain awarded to David Luiz," a FIFA spokesperson said.
"They have studied it and say he definitely had the last touch."
Luis Felipe Scolari's side will face fellow South Americans Colombia in the quarter-final of the competition.