McIntosh first competed for Australia in 1998. At the 2000 Sydney Games, she won three gold medals in the women's 100 m – T38, women's 200 m – T38 and women's 400 m – T38 events, for which she received a Medal of the Order of Australia. She was named the 2000 Junior Female Paralympian of the Year. At the 2004 Athens Games, she won a silver medal in the women's 200 m – T37 event and a bronze medal in the women's 100 m – T37 event, and finished fifth in the women's 400 m – T38 event. despite recovering from a stress fracture in her left foot. At the 2008 Beijing Paralympics, she won two gold medals in the women's 100 m – T37 and women's 200 m – T37 events. She holds the world record for 100 m, 200 m and 400 m T37. She was named the 2008 Female Paralympian of the Year.