The defender, 31, has signed a two-and-a-half year deal at Elland Road after accepting a free transfer from Portman Road.
The lifelong Leeds supporter began his career at Ipswich, where he was club captain, and made more than 300 appearances for the Suffolk side, but he recently fell out of favour under manager Jim Magilton.
He joined Leeds on a one-month loan on January 15 but, after a string of impressive performances at centre-back, he has now agreed to a full-time switch back to his home county.