The 18-year-old catcher was the 21st overall pick in this month's baseball draft out of Lexington, S.C., high school. He led his team to a state championship while hitting .468 with five homers and 33 RBIs this year.
The Gulf Coast Rays begin their regular season in Port Charlotte on Friday.
Ciuffo is the first catcher the Rays have ever selected with their top pick in the draft. He previously had committed to play at the University of South Carolina, which offered him a scholarship at age 14.