 Born in Gondomar, Porto District, Castro joined FC Porto's youth system at the age of 11, from hometown's Gondomar SC.In 2007, he helped the team conquer the junior championship.On 2 February 2008, Castro made his first-team – and Primeira Liga – debut, coming on as a substitute for Paulo Assunção for the last 11 minutes of a 4–0 home win against U.D.