Duffy, 21, was part of the Salford City development squad last season and has previously had trials with Crystal Palace and Brentford.
He starred against the Yellows for Lower Breck in the recent pre-season game and manager Paul Carden was quick to swoop in and secure a deal.
He said: “I did well (last week) and got the call. Me and Ben (Garrity) have had the same type of pathway, it would be good to get a move on to the Football League.
“I’m quite direct, I like to get at players and create chances, hopefully score goals and get plenty of assists. I’ll take every game as it comes.
“Warrington play football. They knock the ball about, they’re organised and tough to break down and look forward to being part of it.”
Keep up-to-date with our exclusive email newsletters.
Subscribe