People began gathering before dawn in Accra's Independence Square wearing Ghana's official colors of mourning -- black and red, the BBC reported.
"I've been here for about three hours, just to see him, but we're really going to miss him here," said a woman who was waiting in a 6-mile line outside the State House in Accra.
Mills, Ghana's third democratically elected president, will be buried in a bird sanctuary at the 17th-century Fort Christiansborg, which overlooks the Atlantic Ocean.
Among the foreign dignitaries attending the funeral were 18 African heads of state and U.S. Secretary of State Hillary Clinton, Voice of America reported.
Clinton, who is currently on an 11-day, seven-nation tour of Africa, is set to hold talks with Mills' successor, former Vice President John Dramani Mahama.