She emerged as one of the world's top 1500 m runners on the 2012 IAAF Diamond League circuit, she won also overall title of Diamond league 2012: 1500 m. She was second to Genzebe Dibaba at the Shanghai Golden Grand Prix, running a best of 3:59.23 minutes. However, she defeated her rival at the Golden Gala, breaking the Ethiopian national record with a run of 3:56.54 minutes, literally days before receiving Swedish citizenship, then won again at the Bislett Games. Aregawi won both the 800 m and the 1500 m for Hammarby IF in the Swedish team championships on June 20. Representing Ethiopia at the 2012 Summer Olympics, Aregawi ran the fastest time in the 1500 metres competition. However, that was while winning the second semi-final race. In the slow, strategic final, Aregawi came off the final turn a step behind the eventual winner Aslı Çakır Alptekin, but faded badly with 20 meters to go in the final straight, initially finishing fifth. After the race, both Alptekin and silver medalist Gamze Bulut were disqualified due to doping violations. Aregawi was subsequently re-allocated the bronze medal.