Authorities say the man was last seen fishing from his boat near Lanier Beach South on Monday night.
WAGA-TV reports that his boat was recovered Tuesday morning, but there's been no sign of the man, who is in his 40s.
Sgt. Greg Colson of the Georgia Department of Natural Resources tells the Atlanta Journal-Constitution that a caller reported a boat going in circles with no one on board near Bald Ridge Creek.
Members of the DNR, Forsyth County Fire Department, Forsyth County Sheriff's Office and the Corps of Engineers are searching for the missing man.
Few other details were immediately available Tuesday morning.