The 20-year-old, who celebrated his birthday earlier this month, made a strong impression during a winter loan spell at Oakwell, where he scored twice in eight outings.
Toney could make his second ‘debut’ at home to Scunthorpe United tomorrow, with Ashley Fletcher on international business with England U20s.
Toney, who came off the bench for the Magpies in their Premier League game at home to Manchester United in January and is highly thought of on Tyneside, said: “It’s great to be coming back into a strong side who are we’re flying at the moment, so hopefully I can bring something extra to the team and keep them going forward.
“From my first spell here I know the surroundings and the area really well, so this helps me to settle back in and hit the ground running.
“Barnsley are a great side, a great bunch of lads, all young talented footballers and I’m looking forward to being part of that.
“I’m raring to go. It feels great that Paul (Heckingbottom) and Tommy (Wright) wanted me back here and I’m delighted to return, so I just can’t wait to get some goals and repay them and the fans.
“Since I’ve been back to Newcastle I’ve managed to get a few appearances off the bench both in the Premier League and Capital One Cup, so I can add that experience to my game and hopefully that will benefit the team here.”