Born in Madrid, Mateos joined Real Madrid's youth system at the age of 12. In the 2007–08 season he made his senior debuts, playing that and the following two years with the B-team in the third division.
In late January 2010, Mateos was called to the main squad by Manuel Pellegrini for a La Liga match against Deportivo de La Coruña. On 3 April of the same year, he also made the final list for the game against Racing de Santander, but failed to leave the bench on either occasion.
During the 2010–11 pre-season, Real Madrid's first-team coach, José Mourinho, said:
It's a shame Mateos can't join us because I like him a lot. He defends well and knows how to instigate play from the back. That's a trait which we need here at Madrid. With the difficulties we have it is a pity that he can not play, I would like him to be part of the first team.
The coach's statements instigated Real Madrid to sign the player to a professional contract and, subsequently, Mateos was called for the first match of the season against RCD Mallorca. After the departure of Rafael van der Vaart and Royston Drenthe, to Tottenham Hotspur and Hércules CF respectively, he was promoted to the first team, being awarded the number 15 shirt previously worn by the latter.
Mateos made his official debut for Real Madrid on 23 November 2010, against AFC Ajax in the campaign's UEFA Champions League, playing ten minutes in the 4–0 away win. After the match, he said: "I will never forget this day."
On 29 January 2011, AEK Athens F.C. signed Mateos on a six-month loan contract, with the Greek side having an option to retain the player for an extra year. In the summer, however, he moved to Real Zaragoza in the same predicament, making his top flight debut on 11 September in a 0–0 draw at Rayo Vallecano but having the season marred by injuries overall.
In late June 2012, Mateos accepted a return to Castilla for 2012–13, after the reserves promoted to the second level after an absence of five years.
On 2 September 2013, Mateos signed for Hungarian club Ferencvárosi TC. He scored two goals in 21 games in his first season, helping his team to the third position.
On 29 July 2015, Mateos joined Orlando City SC in the Major League Soccer, with general manager Paul McDonough describing him as a "well-versed" player who he expected to "make an impact right away". He was waived on 3 March 2017.As of 3 May 2015
Copa del Rey: 2010–11
Greek Football Cup: 2010–11
Magyar Kupa: 2014–15