Her career began in 1996 carrying out diverse tours, participating in her first international competitions. In 1998, she won two silver medals in the Central American and Caribbean Games in the 400 and 800 meters.
Her first major victory was the gold medal in the 400m at the 1999 Pan American Games in Canada. A year later, she qualified to the 2000 Sydney Olympics going to the 400m finals, finishing with a reasonable 5th place with a time of 49.96 seconds. (After that race, she won 28 consecutive international races before a second-place finish in Rome in July 2004).
In 2001, she won the 400m race in Monaco, one of the two 400m events held at Golden League competitions this year. At the 2001 World Championships in Athletics, Guevara made the finals in the 400m. She came off the last turn leading the race with about 105m to go. Unfortunately, she could not keep the fast pace and was passed by Amy Mbacke Thiam from Senegal and Lorraine Fenton from Jamaica with no more than 20 meters to go. Guevara won the bronze medal posting a season best with a time of 49.97 seconds. In fact, Fenton and Mbacke Thiam also posted personal bests, the last one also being a national record.
In 2002, she won all seven competitions of 400m of the Golden League (Oslo, Paris, Rome, Monaco, Zurich, Brussels and Berlin) sharing the jackpot of one million dollars in gold bars with three athletes. She also won the gold medal at the 2002 IAAF World Cup in 400m and 400m relay, running for the Americas team. She won the 2002 IAAF Grand Prix Final in Paris.
In 2003, she defended her title in the 400m at the 2003 Pan American Games winning the gold medal. She won the 400m race in Zurich, one of the two 400m events held at Golden League competitions this year. Later, on August 27, 2003, in Paris, France, she won the 2003 World Championships in Athletics in the women's 400m. She set a personal record, a national record, and a world leading time, running away from the field in 48.89 seconds. That time currently is, as of 2008, the 9th fastest time in history. She won the 400m at the 2003 IAAF World Athletics Final in Monaco.
Guevara, being the flag carrier for the Mexican team, would make her second Olympic team on 2004 representing her country in the 400 meters. After winning her heat in the first round, and her corresponding semi-final, she would go on to win the silver medal in the final. She won the 400m at the 2004 IAAF World Athletics Final in Monaco.
A year later, at the 2005 World Championships in Athletics, she won the bronze medal in the 400 meters with a time of 49.81 seconds, despite the heavy rainfall.
In 2007, for the third consecutive time, she won the gold medal in the 400 m at the 2007 Pan American Games. In addition, she led Mexico's 4 X 400 m relay team to a second-place finish with an incredible comeback. About a month later, at age of 30 Guevara participated in her fourth World Championships in Athletics in Osaka. She finished in fourth place with a time of 50.16 seconds, a season best. Just beating 24-year-old DeeDee Trotter of the United States by .01 seconds.
On January 16, 2008 she announced her definitive retirement from all competitions due to conflicts with Mariano Lara, the (nowadays former), president of the Mexican Athletics Federation. No help was received at that time by Carlos Hermosillo, director of the CONADE (Comision Nacional de Cultura Fisica y Deporte) who did not act rapidly and the problem only grew bigger and continued for months. Ana finally said: "My retirement from sport in Mexico is now definitive, I contemplated the possibility of participating independently at the Olympic Games but my dream was to participate for my country..."
In 2009, she entered politics, standing as the PRD candidate for Miguel Hidalgo Delegation in Mexico City losing to Demetrio Sodi from PAN. She is a Mexican Senator for the 2012-2018 term having been postulated by the Democratic Revolution Party (PRD), the Labor Party (PT), and Citizen Movement Party.
On December 13, 2016 Ana Guevara was beaten up by four men near Mexico city. She was riding her motorcycle and got struck by a car, four men got out of a car and kicked her and punched her. News created national outrage.