The Australian arrives from the Brumbies on a short-term deal after Newby was ruled out for up to five months with a knee problem which has required surgery.
Salvi, who has represented Australia at Under-21s and A team levels, enjoyed a successful season at Bath before returning to the Brumbies.
And Tigers director of rugby Richard Cockerill is pleased will his latest acquisition - particularly as his squad is already likely to be stretched during the World Cup.
Cockerill said: "We're delighted that Julian has agreed to join us. He enjoyed a very good season in England a couple of years ago and has been a major performer in Australia too.
"Losing a player of Craig Newby's influence and experience is a blow to the squad, especially during a World Cup year when we are likely to be without a number of senior players.
"But we see Julian as a very good addition to the squad. He will join us by the end of July and his previous experience in this country should allow him to fit in pretty quickly."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.