TOKYO — Japanese voters handed a landslide victory to the governing Liberal Democrats in parliamentary elections on Sunday, strengthening the grip of a party that promises accelerated changes to Japan’s economy and a shift away from its postwar pacifism.

By securing control of both houses of Parliament for up to three years, the win offers Prime Minister Shinzo Abe — an outspoken nationalist who promises to revitalize Japan’s deflationary economy and strengthen its military — the chance to be the most transformative leader in a decade. Although a lackluster turnout indicated that Mr. Abe might not have as much of a mandate as his supporters hoped, the margin of victory was large enough to suggest he has an opportunity to also bring stability to the country’s leadership after years of short-lived and ineffective prime ministers.

The win comes at a time when many Japanese seem more open than ever to change, after years of failed efforts to end their nation’s economic slump, and as an intensifying territorial challenge by China has nudged this long pacifist nation toward accepting a more robust military.

Unlike some of Japan’s previous colorless leaders, Mr. Abe, 58, seems eager to become an agent of change. He campaigned on this being Japan’s last chance to regain its economic stature as the country has been eclipsed by China, with Sunday’s victory apparently largely because of the early successes of his bold economic plan, called Abenomics. But his party’s calls to stand up to the Chinese by rewriting Japan’s antiwar Constitution to allow a full-fledged military rather than self-defense forces have raised fears he will go too far and further isolate Japan in the region.