Tykes manager David Flitcroft admitted he was delighted to secure the services of Tunnicliffe, a player he has been tracking for a number of years.
The 20-year-old enjoyed a six-month loan spell at Peterborough last season and will now boost Flitcroft's options as he looks to guide the club away from the Championship relegation zone.
Tunnicliffe could make his debut in Barnsley's crucial clash with fellow strugglers Bristol City at Ashton Gate on Saturday.
But the positive news over Tunnicliffe was tempered somewhat by the news on Golbourne, who has undergone surgery on a knee injury.
Golbourne incurred the problem following a high tackle in Saturday's FA Cup win over MK Dons.
"I'll sit down with Scott at some point and we'll through his objectives for pre-season. It's a massive blow because his form has been incredible," Flitcroft told the club's official website.