The Candystripes have completed the signing of the winger from Airtricity First Division side Longford Town
Speaking to the Derry Journal, Derry manager Declan Devine described the left-sided midfielder as 'one of the best young players' to play in the Airtricity First Division last season and suggested that the Brandywell club beat competition from 'quite a few' Irish clubs in order to secure his signature.
"Thomas is one of a number of players we have been following over the past six or seven weeks," he said. "He was considered to be one of the best young players in the First Division last season when representing Longford Town and he had attracted the attentions of quite a few Irish clubs."
The 21-year-old began his career at St Patrick's Athletic before joining Longford Town and has admitted that he was drawn to the Candystripes because of the club's reputation for preparing players for moves to Britain.
"Derry’s record in preparing players for full-time football across the channel is well known in the League of Ireland," Crawley told the Derry Journal.
He added: "I'm delighted that Derry made the approach as I think the club will suit me and from what I've heard from other players, I’ll be joining a top club with a strong dressing room.
"While the club has now earned a remarkable record for selling players on, Derry City still attempts to remain competitive and I think that’s superb."