Shinzo Abe’s Liberal Democratic Party (LDP) and its coalition partner have a two-thirds majority in the lower house.
The governing Democratic Party (DPJ) suffered major losses in the poll, with leader Yoshihiko Noda stepping down.
Conservative Shinzo Abe, who was prime minister in 2006-07, is expected to form a new cabinet later on Wednesday.
He is seen as a hawkish, right-of-centre leader whose previous term in office ended ignominiously amid falling popularity and a resignation on grounds of ill health.
The grandson of a former prime minister and son of an ex-foreign minister, Shinzo Abe, 58, has pledged to take a tough line in a territorial row with China.
China has urged the new government to take “practical steps” to deal with the dispute over islands in the East China Sea.
Shinzo Abe has also called for Japan’s pacifist constitution to be revised and patriotic sentiment nurtured.
The DPJ was elected in 2009 on its promise to increase welfare spending and break ties between the bureaucracy and big business.
But its failure to deliver on the economy and response to the 11 March 2011 earthquake and tsunami lost it support.
This time round Shinzo Abe campaigned on a platform promising an end to years of economic stagnation, with more public spending and a looser monetary policy.
But some economists say there is little new in Shinzo Abe’s policies, or “Abenomics” as they have been called.
He has also said he would allow nuclear energy a role in Japan’s future despite last year’s disaster.
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