Premier Stephen McNeil announced Saturday that byelections will be held in Dartmouth South, Cape Breton Centre and Sydney-Whitney Pier.
The byelections will take place on July 14.
The Cape Breton riding of Sydney-Whitney Pier was previously held by Gordie Gosse, while Cape Breton Centre was represented by Frank Corbett.
The men, who were both NDP members, both resigned from the legislature in April.
The Dartmouth South riding has been vacant since the death of Liberal member Allan Rowe in March.