The 6ft 4ins midfielder was recommended to the club by former Walsall and Bermuda striker Kyle Lightbourne.
The 18-year-old has been training with the League One Saddlers since appearing in a development squad match in April.
"I've loved it here, the way the club has treated me," he said. "And how the players have welcomed me straight in."
Butterfield will initially work under the vastly experienced John Ward, Walsall's professional development coach.
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Walsall have completed the signing of Bermudian teenager Kacy Milan Butterfield on a one-year deal, subject to receiving international clearance.