Smith only returned to the game following a two-year absence two weeks ago, but the 31-year-old has now decided to hang up his boots for good, after an MRI scan on his ankle came back with negative results.
"Were it not for the fans and my family, I probably would have decided to announce my retirement much earlier due to my injury," Smith told Die Volksblad.
"But it was the fans who helped me muster the courage every time after the disappointment of an operation to return to the football field to try again this year.
"I appreciate all the support that I have got with my family over the years from Bok and especially Free State [Cheetahs] fans."
Smith represented the Springboks 69 times between 2003 and 2010, scoring 60 points at senior international level.