Fergus shot 2-under-par 70 to finish at 12-under 204 overall, and won despite bogeys on two of the final three holes.
"When your time comes, it just seems like it happens," said Fergus, who started the final round with a one-shot advantage. "I just hung around, hung around and it happened. The last three or four holes are tough (and) when you're trying to win your first tournament, you let a few get away."
Fergus claimed a winner's check of $375,000 and joined Ron Streck as the only players to win on the Champions Tour, PGA Tour and Nationwide Tour.