Montañés began playing tennis at the age of six. In 1999 he turned professional.
In 2001 he beat Michael Chang and Karol Kučera at the ATP tournament in Estoril before losing to Juan Carlos Ferrero . In the same year he reached the third round of the French Open , which he was able to repeat in 2002. In the same year he was able to defeat the former number 1 in the world, Gustavo Kuerten , at the ATP tournament in Rome . In 2001 he was in the top 100 of the world rankings for the first time .
In 2004 Montañés reached the second round of Wimbledon , in which he was defeated by Alexander Popp . In 2005 he moved into the second round of the US Open . In 2006 and 2007 he again reached the third round of the French Open. On August 2, 2010, Montañés was 22nd in the tennis world rankings, his best placement. During his career, he won six singles titles and another two doubles. In his second career title in 2009 in Estoril , he was able to fend off match points in the quarter-finals and the final, a feat that only a few players before him managed to do. He also holds the inglorious record for most first round defeats in Grand Slam tournaments . Between 2001 and 2016 he went 35 times as a loser in 53 tournaments after the first round.
After Montañés had to admit defeat to his compatriot Feliciano López 2: 6, 2: 6 in the second round of the Barcelona Open , he ended his professional career after 18 years.