The measures, approved overnight, introduce a new top tax rate of 42% for Greeks earning more than 42,000 euros ($56,000) a year.
Corporate rates also go up and the tax base now includes low-earning farmers.
Greece has been kept solvent by huge rescue loans from its EU partners and the IMF since May 2010.
The Conservative-led government insists the new measures, designed to raise up to 2.3 billion euros this year, are fair.
“We are not in favor of taxes,” Deputy Finance Minister Giorgos Mavraganis said.
“But in the current situation we must lead the country out of its impasse.”
The changes are part of an overall package approved in November to allow Greece to qualify for further bailout funds.
But the opposition says the tax rises will increase hardship for ordinary Greeks. The main opposition Radical Left Coalition says austerity has “demolished the country’s middle classes”.
Deep spending cuts and job losses have triggered street unrest across Greece in recent years.
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