South Africa have flown in Van Jaarsveld as a back-up for injured captain Graeme Smith who is unsure for Sydney.
Smith, who made 48 and 101 in his side’s six-wicket win in the first Test in Perth last week, has lined up for the second Test at the MCG only after having further treatment on his elbow.
Van Jaarsveld, a hard-hitting left-hander, will arrive in Australia tomorrow.
The uncapped 23-year-old was originally scheduled to land with the one-day squad in the second week of January.
"Vaughn (Jaarsveld) will provide us with cover for both Ashwell Prince and Graeme Smith. It will also provide him with a valuable opportunity to work with the national squad as he is the only member of the one-day international squad who did not attend our pre-season camp in October," coach Mickey Arthur said.
Prince, who has missed the first and second Tests with a thumb injury, was replaced by JP Duminy.
The third and final Test starts in Sydney on January 3. Australia will also host the Proteas for two Twenty20 internationals on January 11 at the MCG and two days later at the Gabba.
A five-match one-day series kicks off on January 16 at the MCG.