While it was previously known the couple would wed, Peladeau, 53, announced the Aug. 15 date in an interview with Paris Match on Thursday.
Snyder, 47, is a well-known TV personality in Quebec and has been with Peladeau for about 15 years.
They have a son and daughter together, while Peladeau also has a daughter from a previous relationship.
The wedding will take place three months to the day of Peladeau becoming PQ leader.
Peladeau is the controlling shareholder of Montreal-based media conglomerate Quebecor Inc. (TSX:QBR.B).