Top scorer for Cheltenham Town for 2011-12 season, Duffy started his career for Rangers and has played for major sides such as Hull City and Swansea City.
Duffy, who has been training with Salgaocar for a week, said, "The coach is doing a lot of things for us, inculcating good sleeping patterns, eating habits. The training system is mostly the same. The players are a friendly bunch, they're really nice and I'm looking forward to playing with them."
Rhys Mascarenhas, Duffy's manager, said, "Salgaocar were looking for a good striker. With his experience, I'm sure Darryl will play an important role in the first team this season.