The 34-year-old will link up with Tigers from Castres, having featured in last Saturday's Welford Road friendly against Nottingham.
Laussucq made three Test appearances, including starts against Scotland and Ireland during the 2000 Six Nations tournament.
He was also part of the Stade Francais squad that won two French Championship titles.
Leicester's acting head coach Richard Cockerill said: "It is no secret that we have been looking for some experienced competition for the scrum-half spot with Harry Ellis and Scott Bemand sidelined by injury for a decent length of time.
"Christophe certainly has the experience gained at the top level in France.
"He did a decent job on Saturday after coming in at short notice, and now we are looking for him to join the pre-season work, settle in quickly and join Frank Murphy and Ben Youngs in the frame for that number nine shirt."