The media mogul, who entered politics during the last provincial election under then-Premier Pauline Marois, said at a press conference in Montreal Monday he was quitting for family reasons.
Looking sombre, Péladeau said he had to choose between his family and his political life.
“I chose my family,” he said in French.
“I am immediately quitting as Parti Québécois leader, the official opposition, and as the representative of Saint-Jérôme.”
Péladeau called the decision agonizing, and appeared to be fighting back tears as he made the announcement.
“I am making this decision for the well-being of my children,” he said.
“I must remain an example to them.”
He took no questions.
After being elected, Péladeau was hailed by many as the saviour of Quebec’s sovereigntist movement.
In a recent CROP poll, support for the PQ dropped four percentage points since March, with 26 per cent of those asked saying they would vote for the separatist party.
In the party’s leadership race to succeed Marois last May, Péladeau was easily elected with 57.6 per cent of the vote.