Her first major competition representing Ethiopia was the 1999 IAAF World Half Marathon Championships, where she finished 38th overall at the age of sixteen. She improved to 20th place at the 2001 edition of the event, helping the Ethiopian women to the team bronze medal as a result. In the following year at the 2002 IAAF World Cross Country Championships she finished tenth and took the gold medal in the team competition with Ethiopia. She returned to the World Half Marathon Championships in 2003, but did not repeat her medal success, finishing in 21st place and fourth overall with the women's team. One of her first ever road racing wins was at the Marseille-Cassis Classique Internationale in 2003, where she finished the half marathon in 1:10:07. In the 2004 season Erkesso took on both the long and short races at the 2004 IAAF World Cross Country Championships in Brussels. After finishing fifth in the long race and winning the team gold, she reached the global podium for the first time with a bronze medal in the short race and yet another team gold. She won the IAAF's Lotto Cross Cup Brussels cross country meeting twice consecutively in 2005 and 2006. She again ran in two races at the 2006 IAAF World Cross Country Championships, but was less successful on her second attempt. Although she finished twelfth and won a team gold medal in the short race, she was well off the pace in 46th position in the long race. Erkesso was victorious at the Vancouver Sun Run 10K in 2007, and won the 2009 Bay to Breakers with a time of 38:29. That same year she just missed out on the podium at the Chicago Marathon, finishing in fourth place. She won the 2009 Houston Marathon in a state record time and improved it further with a second win in 2010, running 2:23:53. She set a new personal best at the Ras Al Khaimah Half Marathon in 2010, taking fourth place with a time of 1:07:41. She won her first World Marathon Major in April that year, winning the Boston Marathon with a time of 2:26:11. She led from the halfway point and increased her lead, just managing to hold off Tatyana Pushkareva in the final stages. In June she took part in the Freihofer's Run for Women and finished in fourth place, some distance off the winner Emily Chebet. She missed almost all of the 2011 season, with her sole appearance coming at the 2011 Boston Marathon, where she failed to finish. She also pulled out early on in her first race of 2012 at the Ottawa Marathon.
