The 31-year-old made 23 appearances for the side in a spell there earlier in the season, scoring one goal, before the loan deal expired on January 8.
He made a total of 42 appearances for Scunthorpe, including 25 league starts, scoring two goals since his switch from Preston North End in May 2015.
King, who can play in defence or in midfield, returns to the Boro ahead of their League Two encounter away at Crawley Town at the weekend.
Stevenage then welcome Wycombe Wanderers and Cheltenham Town to Broadhall Way, looking to back up their latest victory - a 2-0 triumph over Grimsby Town.
The club would like to place on record their thanks to Jack and wish him all the best for the future.
