The 36-year-old, who has scored three goals in 36 appearances this season, moves to Hillsborough until the end of the current campaign.
Howard began his professional career with Pools in 1995 before spells with Northampton and Luton. He was then a Championship regular with the likes of Derby and Leicester.
After 146 appearances and 28 goals for the Foxes he re-joined Hartlepool in the summer of 2012.
Howard is eligible to feature on Saturday when the Owls face Barnsley at Hillsborough.