The 22-year-old dreadlocked singer-songwriter, who finished fourth on Season 7 of American Idol, wed girlfriend Mandy Mayhall in his hometown near Dallas.
"Yesterday I married the girl of my dreams," he tweeteed Sunday. "It couldn't have been more perfect! Now, honeymoooon!!! :)"
Earlier this week, the groom-to-be enjoyed a bachelor party complete with bowling, poker and pool, according to his own posts.
The couple confirmed their engagement in November. Castro reportedly proposed on Halloween while the two were dressed as characters from Disney's Beauty and the Beast.
On Jan. 12, Castro will release The Love Uncompromised EP on Atlantic Records, followed by a full-length album in the spring. After spending some time with his new bride, he'll kick off a tour later this month.