The South African will arrive on January 1 and should provide added strength in depth, given James Simpson-Daniel and Mike Tindall could be called up for RBS 6 Nations duty by England.
Coach Dean Ryan is delighted to welcome the 28-year-old to Kingsholm and told www.gloucesterrugby.co.uk: "The opportunity came along for us to sign Rudi and it was simply too good to turn down.
"He is an exciting player, comfortable at either 12 or 13, I am sure he will be a very good acquisition for us.
"He has Super 12 experience and that is always a quality worth pursuing.
"It is very important we don't expose ourselves and threaten the overall strength of the squad during periods when we could lose players."