The Bears also locked up defensive tackle Israel Idonije with a two-year extension through 2011 and agreed to contracts with seven of their nine draft picks.
The 6-foot-1, 240-pound Tinoisamoa led the Rams with 135 tackles (88 solo) before getting released by a new coaching staff seeking more size. In Chicago, he's reuniting with coach Lovie Smith, his defensive coordinator during the 2003 season in St. Louis.
Tinoisamoa will probably start at strongside linebacker alongside Lance Briggs and Brian Urlacher, although incumbent Nick Roach and former starter Hunter Hillenmeyer are in the mix. A second-round pick by the Rams in 2003, he has 661 total tackles, 10 sacks, seven interceptions, 25 pass break-ups, six forced fumbles and three fumble recoveries in his career.
Besides reeling in Tinoisamoa, the Bears committed to an important part of their defense in Idonije, who posted career highs with 28 tackles and 3½ sacks last season.
They also agreed to terms with all but two of their draft picks: cornerback D.J. Moore, wide receivers Johnny Knox and Derek Kinder, linebacker Marcus Freeman, safety Al Afalava, tight end Lance Louis and defensive end Henry Melton. Still unsigned are defensive tackle Jarron Gilbert and wide receiver Juaquin Iglesias.