Defender Tony Vaughan, 28 has joined the Reds on a free transfer from Mansfield Town.
Vaughan had previously played under Paul Hart at Forest and the Reds manager told the official Barnsley website:"I know Tony very well and I can recognise the vital ingredients he'll bring to the club.
"He's a tough competitor who is desperate to enjoy success with us. His hunger and tenacity shine through when you talk to him. Many players may be on their summer breaks, he's counting the days to pre-season training and to get out there in a Barnsley shirt."
Vaughan and Bobby Hassell who signs for the Reds next week were part of the side defeated by Huddersfield in the Third Division play-off final.