The 20-year-old dreadlocked Texan gave two disastrous performances on the Rock and Roll Hall of Fame themed night and found himself voted into the bottom two with Syesha Mercado.
His rendition of Bob Marley's 'I Shot the Sheriff' was branded "really karaoke" by judge Randy Jackson, while Simon Cowell bluntly told him his version was "utterly atrocious". After forgetting the lyrics to Bob Dylan's 'Mr. Tambourine Man' for his second song, Cowell told Castro to "pack your bags".
Commenting on his Tuesday night performances, Castro said: "It's just getting tough for me. I think my inexperience is coming in. This week I tried to pick two [songs] I knew and even that, I screwed it up."
Castro's departure leaves Mercado, David Archuleta and David Cook as the three remaining American Idol contestants.