The coach was captured in a video receiving cash from investigative journalists posing as football agents who requested that two players be selected for a major championship.
“For now, the NFF has commenced preliminary investigation into the matter to assist the Committee on Ethics and Fairplay,” NFF director of communications Ademola Olajire said in a statement.
The names of the players were not disclosed and Yusuf, 56, who was assistant to Gernot Rohr at the recent World Cup in Russia, has denied any wrongdoing.
He said the money was a gift and that the players were selected on merit.
The country’s football coaches association has said it stood by the Yusuf, who led Nigeria to the final of this year’s Championship of African Nations in Morocco.