Born in Valtierra, Castillejo started his football career with local CA Osasuna, being mainly associated with the reserves and scoring 20 Segunda División B goals with them in the 1992–93 season.
[1] He made his La Liga debut with the first team on 14 March 1993, appearing as a late substitute in a 1–0 home win against Real Zaragoza,[3] and featured in just ten games in his only full campaign, which ended in relegation; he was also loaned to Deportivo Alavés during his spell.
Released by the Navarrese in summer 1996, Castillejo resumed his career in the Segunda División but also in the third tier, with CD Numancia,[4] CD Castellón, Gimnàstic de Tarragona[5]– he netted 21 times as the club achieved promotion to division two in 2001, best in Group III, second overall – UB Conquense, CD Leganés and CF Reus Deportiu, retiring in 2008 at the age of 37.
[6] Castillejo started working as a manager immediately after retiring, initially being an assistant with Reus in Tercera División.
[7][8] Castillejo agreed on a return to former club Gimnàstic in late May 2013, signing ahead of the 2013–14 campaign.