General Mahamat Idriss Deby Itno will be replacing his father, Idriss Deby Itno, as head of a military council.
The army announced on Tuesday in a radio broadcast that the four-star general will replace his father.
The newly re-elected President died of injuries on Tuesday while fighting rebels in the north of the Sahel country.
The shocking announcement came only the day after the 68-year-old was proclaimed the winner of a presidential election that had given him a sixth term in office.
The army said Deby had been commanding his army at the weekend as it battled against rebels who had launched a major incursion into the north of the country on election day.
