The 28-year-old Kiwi has won two Super Rugby titles with the Chiefs since 2012.
Fitzgerald is the latest Antipodean to move to Welford Road following Monday's arrival of Peter Betham from New South Wales Waratahs.
"Mike will be a good addition to our group of locks, especially with the retirement of Louis Deacon and Brad Thorn," director of rugby Richard Cockerill is quoted as saying by Sky Sports News. "He has played in very good company at the Chiefs, and now wants the experience of playing rugby in Europe."
Leicester continue their Aviva Premiership campaign on Saturday when they host London Welsh.