The Owls Academy graduate penned a two-and-a-half-year professional deal at Hillsborough in November 2013 and has been recognised at youth level for England.
"I'm excited to get started," Wildsmith told barnsleyfc.co.uk. "It's an ideal opportunity for me, living close by, and I'm looking forward to working with Mark Crossley again and help push the lads on."
The goalkeeper has been handed squad number 13 ahead of the Reds' trip to Bristol City.
