Moreau, 55, will be the second person to present an official candidacy to replace former premier and party leader Jean Charest.
Former finance minister Raymond Bachand confirmed his spot in the race on Friday.
Former health minister Philippe Couillard is expected to make his own announcement on Tuesday or Wednesday in Montreal.
Moreau was elected for the first time in 2003, but was defeated in 2007.
Between 2007 and 2009, he acted as chief of cabinet for the parliament leader. He did, however, get re-elected as member of national assembly in 2008 and 2012.
Some say Moreau's age makes him a member of a "new generation" of Liberals.
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