Jake Lehmann, son of Australia coach and former Yorkshire batsman Darren, has joined the White Rose county until the end of the current season.
The 24-year-old replaces Travis Head, who was called up to the Australia squad on Monday, but is not eligible to play in limited-overs cricket.
He averages 41.05 from 19 innings for South Australia in first-class cricket.
Former Australia international Darren scored over 14,000 runs for Yorkshire in nine seasons with the county.
"We're very fortunate that we've been able to find a replacement quickly for Travis Head, who's got a deserved call-up to the Australian squad," Yorkshire coach Jason Gillespie told BBC Radio Leeds.
"I know the Yorkshire supporters will be buzzing about the fact that it's another Lehmann on the scorecard, but he's his own man.
"He's a wonderful young player. He hasn't played a lot of first-class cricket, but he's made a real impact with South Australia and Australia A very early on."
Yorkshire, who are chasing a third County Championship title in a row, have six four-day games left this year starting with the Roses match at Old Trafford which gets under way on Saturday.