The 23 year-old has been on loan with the Tykes since late October, helping Lee Johnson’s side move clear of the relegation zone.
The winger has made 13 appearances in total for the League 1 side, putting in man-of-the-match performances against Blackpool and Fleetwood.
The extension of his loan deal will give Isgrove the chance to reach his second Johnstone’s Paint Trophy final.
Barnsley drew 1-1 with Fleetwood in the first leg of their area final, with the second leg set to take place at Highbury on Thursday 4th February.
Isgrove will hope to be in action on Saturday when Barnsley welcome Rochdale to Oakwell.