She entered the senior ranks fully in the 2003 season. She placed third in the 800 m at the Brazilian Athletics Championships, but showed new strength in the 1500 metres discipline by winning her first national title in a personal best of 4:19.16 minutes at the distance. At the 2003 South American Championships in Athletics she was dominant in the longer event, setting a personal best and championship record of 4:17.54 minutes to win by a margin of four seconds over runner-up Niusha Mancilla. She did not appear internationally in 2004 but retained her national title in 1500 m and ran an 800 m best of 2:02.60 minutes. She repeated that feat the following year, winning a third straight Brazilian title and an improvement to 2:01.25 minutes. At the 2006 Brazilian Championships she secured an 800/1500 m double, including a new best of 4:16.25 minutes over the longer distance. She returned to the top of the regional scene with two gold medals at the 2006 South American Championships in Athletics, first in the 1500 m and then in the 4×400 metres relay which the Brazilian women won by several seconds.
Pan American champion
She married fellow Brazilian runner Marílson Gomes dos Santos around the start of 2007 and began competing under her married name, Juliana Gomes dos Santos. A fifth straight title in the 1500 m came at the Brazilian Championships that year and she was selected to run at the 2007 Pan American Games. There she became the first South American woman to win the 1500 m Pan American title, seeing off American Mary Jayne Harrelson by a margin of nearly two seconds. Hers was one of nine athletics gold medals for the hosts in Rio de Janeiro. She ran in the 800 m heats the same day, but did not make the final of that discipline. She ran in Europe that June a set a personal best of 4:11.39 minutes in Neerpelt. Santos won another 1500 m national title in 2008, but did not compete internationally over the following seasons and missed 2009 entirely. She returned to action in 2010 and ran a Brazilian record time of minutes in the 1500 m to claim the silver medal at the 2010 Ibero-American Championships in Athletics. However, this was a brief resurgence as she did not compete after that event and missed the 2011 season. The highlight of her 2012 was a middle-distance double at the Brazilian Championships. Santos made her first international appearance in cross country running at the 2013 IAAF World Cross Country Championships and on her first attempt placed 69th in the women's race. She ran a personal best of 16:56.73 minutes for the 5000 metres of the track that summer. Two international medals came at the 2014 Ibero-American Championships in Athletics, held on her home area of São Paulo. She was the bronze medallist in the 1500 m and successfully stepped up a distance with a gold medal over 3000 metres. In spite of this success, when it came to the national stage she was relegated to runner-up in both middle-distance track events, losing to Jessica dos Santos in the 800 m and Flavia de Lima in the 1500 m.