Defar won the 5000 metres gold medal at the inaugural Afro-Asian Games in 2003. She won gold medals in the women's 5000 metres at the 2004 Summer Olympics in Athens with a time of 14:45.65 and 5000 metres at the 2012 Summer Olympics in London. She also won bronze medal at 2008 Beijing Olympics, which turned in a silver medal after the disqualification of Turkish athlete Elvan Abeylegesse.