Mitchell competes in javelin. As a fourteen-year-old, she started in the sport but did not begin to take the sport seriously until she was seventeen years old. She took up the sport after her sister borrowed a javelin from school to practice with it for a school event. Mitchell was coached by Lindsay Burgoyne in high school. At the start of high school, she broke the school record by. She was coached by Eric Hollingsworth from 2003 to 2009. Uwe Hohn has been her coach since 2010. She trains at Olympic Park in Melbourne and has a scholarship with the Victorian Institute of Sport. She is a member of the Eureka Athletics Club. In 2006, Mitchell represented Australia at the Commonwealth Games, where she made the finals in the javelin, finishing sixth overall. She finished first at the 2008 National Championships in Melbourne, Australia. In 2010, she set a Victorian state record in the javelin. At the 2010 Commonwealth Games, she finished fifth. Prior to competing in India, she spent four weeks training in Germany. She finished second at the 2011 National Championships in Melbourne, Australia. In January 2012, she competed at an Athletics Victoria inter-club meet, where she made a throw of. While this distance would have qualified her for Olympics, the nature of the meet precluded it from counting. She finished second at the 2012 National Championships in Melbourne, Australia with a throw of, short of the Olympic A-Qualifying distance of. She finished third at the 2012 Ostrava Golden Spike in Ostrava, Czech Republic. At the event, she threw a personal best throw of. In April, she finished second at the 2012 St. Wendel World Class Meeting in Germany. She was selected to represent Australia in the javelin event at the 2012 Summer Olympics, where she qualified for the final in the women's javelin. Before departing for London, she participated in a Germany-based training camp. At the Rio Summer Olympics in 2016, she placed 6th in the javelin throw final, with an effort of 64.36m. Mitchell competed at the 2014 Commonwealth Games, finishing fourth, with a best throw 36 cm less than that of bronze medal winning compatriot Kelsey-Lee Roberts. She improved on this performance at the 2018 Games, winning gold with a throw of 68.92m and setting a new Commonwealth Games record.
