Don Elgin was born in 1975 in the Victorian town of Donald. He was born without a left leg and a left thumb, with small toes, and webbed fingers on both hands; his malformed left foot was amputated shortly after he was born and he had open heart surgery at the age of three. He competed in athletics and swimming as a teenager.
Don Elgin first participated in sports for people with disabilities at the 1990 New South Wales Amputee Championships. His first international competition was the 1994 IPC Athletics World Championships in Berlin, where he won a gold medal in the 4x100 m relay and a bronze medal in the high jump. He participated without winning any medals at the 1996 Atlanta Paralympics and came fourth in the pentathlon At the 1998 IPC Athletics World Championships in Birmingham.
At the 2000 Sydney Paralympics, he won a bronze medal in the Men's Pentathlon P44 event. At the 2002 IPC Athletics World Championships in Lille, he won two silver medals in the pentathlon and 4x400 m relay and a bronze medal in the 4x100 m relay. At the 2004 Athens Paralympics, he won a silver medal in the Men's 4x400 m T42–46 event and two bronze medals in the Men's 4x100 m T42–46 and Men's Pentathlon P44 events. He came sixth in the pentathlon at the 2006 IPC Athletics World Championships, where he was the Australian flag-bearer at the opening ceremony, and commentated at that year's Commonwealth Games in Melbourne. He retired from para-athletics in 2008, but made a comeback in 2013 after learning that the sport would be included in the 2014 Glasgow Commonwealth Games. He came eighth in the Men's Discus Throw F42/44 at the games.