The frontman has spent the first half of the campaign with another third-tier side, Shrewsbury Town, netting seven goals in 26 outings for the Shropshire outfit.
20-year-old Toney has made a handful of substitute appearances for Newcastle at first team level, having joined from Northampton Town in 2015.
He links up with a Scunthorpe side sitting second in League One, the Iron managed by former Burnley defender Graham Alexander.