James has continued to work out during the summer after negotiations with the Marlins came to a halt.
Initially an Oklahoma State signee, James had explored the possibility of going to a junior college in case he was unable to reach an agreement with the Marlins before the deadline. Going to a junior college would've left James the option of entering next year's draft.
The Marlins have deep connections in the state of Oklahoma.
Marlins owner Jeffrey Loria formerly owned the Oklahoma City 89ers, scouting director Stan Meek lives in Norman and served as OU's pitching coach for 14 years, vice president of player development Jim Fleming lives in Purcell and the team's No. 1 starter, Josh Johnson, is from Jenks.
"One of the main reasons I decided to sign was the Marlins' great track record of developing pitchers," James said. "I'm looking forward to learning from some of the best coaches in the game."