Castillo made his debut for Vida in the top flight of Honduran football on 27 September 2008. He scored his side's only goal in a 1–1 draw with Hispano.[1]
On 22 June 2012, Castillo joined Deportes Savio on loan until the end of the year. He made his debut on 30 July, starting in the opening match of the Apertura tournament in a 3–1 loss to Olimpia.[2] He would score his first goal the following 12 August in a 4–2 away defeat to Platense.[3][4]
On 12 August 2018, Castillo scored the winning goal in the F.C. Motagua's 1–0 victory over Real C.D. España. With this goal, he became the club's all-time scorer with 77 goals. This also represented his 100th goal in Liga Nacional.[5] After his performance at the 2018 CONCACAF League, he was nominated for Player of the Year and was also included in the Best XI at the 2018 CONCACAF Awards.