The defender has signed a new 18-month contract and is now tied to the Edinburgh club until summer 2022.
After a series of convincing displays since his arrival in October, Hearts fans were keen for him stay beyond the end of the campaign.
Kingsley signed as a free agent on a deal running through to the end of the current campaign, but that has now been replaced with the new 18-month agreement.
The 26-year-old is the established first-choice left-back in manager Robbie Neilson’s defence as Hearts target promotion back to the Premiership.
“I’m delighted that we’ve got this one over the line,” Neilson told the Hearts website. “Stephen is a top quality player and has made a real impact since joining the squad.
“I know he’s popular with the fans and it’s great that they will get to see him pull on the maroon jersey for another 18 months and, of course, it’s a real boost for us to retain the services of a top, top player.”
Left-back had been something of a problem position for Hearts in recent seasons. Following Aaron Hickey’s transfer to Bologna last year, Kingsley has fitted seamlessly into the position.
He has scored five goals in 16 games so far this year. The Scotland internationalist is keen to play at the top level and will hope to complete a Championship title triumph in Gorgie by the end of April.