The official Agência Brasil news service said Enel Brasil agreed to pay 2.19bn reais (US$640mn) for the company, previously controlled by state-run group Eletrobras alongside Cia Celg de Participações.
A minimum price of 1.79bn reais had been set by the government.
An initial privatization auction scheduled for August was postponed after it failed to attract offers.
"The new controller will have to meet new performance targets in the next five years, showing a substantial improvement in service," Agência Brasil said.
Celg-D distributes electricity to 2.61mn customers across 237 municipalities in Goiás state, covering an area of 336,871km2.
Eletrobras hopes to follow the Celg-D auction by offloading six other distribution companies as it shifts its focus to generation and transmission.