A knee injury sustained by second-choice keeper Jack Walton in the midweek Checkatrade Trophy win over Bradford City - which has ruled him out of this weekend’s Roses game - has prompted the move for Smith, with regular keeper Adam Davies on international duty with Wales.
Derbyshire-born Smith, 23, a 6ft 1in keeper, has made 44 appearances for Forest in total and spent loan spells earlier in his career at Ilkeston and Nuneaton Town.
Smith made 32 appearances for Forest last term, with his final appearance coming in the 3-0 home loss to Preston at the end of January.
“It’s really unfortunate that both our senior goalkeepers are unavailable at once, but these situations can happen in football,” said Barnsley chief executive Gauthier Ganaye. “We’re really thankful to Nottingham Forest for allowing us to take Jordan on-loan, they’ve helped us out when we needed it. We’re really pleased to be able to bring in a goalkeeper with Jordan’s experience at such short notice.”