The 28-year old defender was released by Rangers on the final day of the January transfer window, therefore was free to join any club that was interested despite the deadline closing.
But Walter Smith only used Webster once in the league in the first six months of this term and he will now serve Jim Jefferies as Hearts strive to stay in touch with the Old Firm rivals Rangers and Celtic.
"I am delighted to have rejoined Hearts and am very grateful to the manager and owners for giving me the chance to return to a club that means a lot to me," he told Hearts News.
"A lot was written at the time I left and the circumstances were indeed unfortunate, but the fact I have returned to a club which means so much to me - particularly when there were opportunities at other clubs - says everything I need to say on my return.
"Now my entire focus is on the future and helping Hearts secure European football."