Established Premiership players Neil Briggs, Gonzalo Comacho, Jamie Gibson and Ryan Lamb will all move to Welford Road, together with Scarlets fly-half Owen Williams.
Hooker Briggs arrives from London Welsh after previous experience with Sale Sharks, Rotherham and French club Bourgoin. An England Saxons cap, the 27-year-old made 15 Aviva Premiership appearances with Welsh in 2012/13.
Back-rower Gibson, 22, is also a Saxons cap and moves to Tigers after 70 appearances in three seasons with London Irish.
Fly-half Lamb, 27, made more than 50 appearances in two years with Northampton Saints after spells with Gloucester and London Irish. As well as two Churchill Cup campaigns with the England Saxons, Lamb has been involved in two Premiership Finals against Tigers, for Gloucester in 2007 and with Northampton this year.
Argentina international wing Gonzalo Camacho, 28, joins his third English club after a spell with Harlequins – scoring the winning try in the Amlin Challenge Cup Final in 2011 – and two years with Exeter Chiefs.
The fifth new signing is 21-year-old fly-half Williams, a former Wales Under-20 international. After playing his early rugby with Ystradgynlais, he played age-group level with the Ospreys before gaining senior experience with Llanelli, including the 2012 Premiership Final, and the Scarlets for whom he scored 21 points in an LV= Cup win over the Tigers last October.
Tigers director of rugby Richard Cockerill said: “It is important that we have good strength and depth in our squad to keep us competitive through a long season and we feel the new signings can all make a big contribution here.
“Four of those players have extensive Premiership experience, which is important, while Owen Williams is a young man with a lot of ability and potential which we believe can be developed within the Tgers squad.”
Tigers have already confirmed the arrival of prop Jerome Schuster and scrum-half David Melé from French club USA Perpignan.
