Webster, 27, almost joined United from Arbroath in 2001 but instead elected to go to Hearts, at that time managed by current Tannadice boss Craig Levein.
A highly successful period at Tynecastle saw him capped 22 times by Scotland before moving to Wigan in 2006.
A permanent transfer to Rangers in 2008 followed an initial loan period, but the stopper's first-team appearances have since been restricted due to injury.
Webster, however, returned to the international scene in May, playing and scoring for Scotland B against Northern Ireland B.
Levein was pleased to renew his relationship with Webster, saying: "Andy Webster is a player I know very well, having signed him for Hearts back in 2001.
"He is a player I know can play at the highest level and I wasn't surprised to see him return to the international scene at the end of last season.
"He now needs regular first-team football to build on this and this loan arrangement will benefit him and, of course, Dundee United.
"For our part, he will further strengthen a very important area of the team and add to the options I have defensively.
"For his part, it gives him an opportunity to gain regular first team football and get his career back on track after overcoming his injury problems."
Source: Team_Talk