Speaking in Montreal, Mulcair said the Conservatives under Stephen Harper have ignored the problem of global warming.
"He sees no urgency to act," Mulcair said.
"After a decade of time wasted under Stephen Harper, we need a prime minister with the long-term vision to fight climate change."
Mulcair's announcement Thursday made mostly in French came in a riding the New Democrats took from Bloc Quebecois Leader Gilles Duceppe in the last election.
This election features a rematch as Duceppe fights to win back Laurier-Sainte-Marie from incumbent Helene Laverdiere.
That battle is now playing out against a backdrop in which polls suggest support for the New Democrats in their key Quebec base is slipping. It was the NDP surge in Quebec in 2011 that propelled the party into Official Opposition status for the first time ever.
Mulcair, however, has been insistent that his party has never enjoyed stronger support in the province and has been, outwardly at least, confident his party will do well.
Mulcair was introduced Thursday by Anne Lagace Dawson, who is taking on Liberal Leader Justin Trudeau in Papineau.
The NDP leader, who has been talking about fighting greenhouse-gas emissions and global warming all week, said he would spend $200 million over four years to help retrofit 50,000 homes and 15,000 apartments to make them more energy efficient.
That, he said, would save homeowners and renters money, and help save the environment.
Mulcair also pledged $150 million over four years to a green municipal fund. The money would offer local governments stable funding for sustainable projects and cleaner transit.
He also promised to set new targets to electrify government vehicles and to set up 150 electric-car charging stations on federal properties.
"An NDP government will be good news for towns, cities and the families who call them home," Mulcair said.
The pledges follow earlier promises to bring in a cap-and-trade plan and carbon pricing to bring down harmful emissions.
On Friday evening, Mulcair will get to make what could be his last French-language pitch to the entire province when he takes on the other leaders in a televised debate.
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