Castillo joined Botafogo on 2 January 2008 for an undisclosed sum and presented on 6 January. He played in every game that Botafogo won during their success in the Copa Peregrino, against Stabæk and Viking. He helped the club to win the friendly tournament, not conceding goals in the two matches that the club disputed. Thanks for his performances on 22 January 2008, was nominated to the Uruguayan national football team by Oscar Tabárez for a friendly against Colombia on 6 February.