Members of the lower house, State Duma, said the repeated requests from the separatist regions for their independence to be recognized "have legal grounds and are morally justifiable."
Hundreds of civilians were killed in South Ossetia, the regional capital Tskhinvali was devastated, and thousands of locals were forced to flee when Georgia launched an attack on August 8 to seize control of the region.
Russia retaliated with an operation to "force Georgia to accept peace." Georgia's ally the United States and other Western powers accused Moscow of a disproportionate use of force, and NATO froze ties with Russia last week.
Lawmakers said the recognition of the republics will help ensure security and protect people in Abkhazia and South Ossetia "from threats from third countries."
A similar resolution was unanimously passed earlier on Monday by the Federation Council after the upper house said that by using force against South Ossetia, which also reignited the conflict with Abkhazia, Georgia had lost the moral right to seek control of the breakaway provinces.
The military offensive "definitively deprived the Georgian leadership of the right to push for the South Ossetian and Abkhazian dependence on their adventurist polices, which have led to a humanitarian catastrophe," the Federation Council said.
The State Duma also appealed to the United Nations and other organizations to back the de facto independent regions and exert pressure on Georgia to end the crisis.
"The State Duma is appealing to parliaments of the UN member states and international parliamentary organizations to recognize Abkhazia and South Ossetia as independent and sovereign countries," the resolution said.
The State Duma said Western states' "unequivocal" support for President Mikheil Saakashvili's regime, which had "prepared for war using the cover of democratic slogans," was partly to blame for the conflict.
Lawmakers also criticized Western media bias in favor of Georgia and accused the Council of Europe and the UN Security Council of failing to speak out to protect South Ossetians "who were dying under bombs and bullets."
The leaders of Abkhazia and South Ossetia, which broke away from Georgia after bloody post-Soviet conflicts in the early 1990s, spoke in Russia's upper house on Monday and appealed for lawmakers to support their independence. Many people in the regions hold Russian citizenship.
The separatist leaders earlier requested Moscow to allow the regions to become part of Russia, however, Moscow did not formally grant the request. Georgia accused Russia of supporting the separatist regimes and attempting to annex its territory.
Russia has now withdrawn most of its troops from Georgia, but peacekeeping checkpoints are still in place as Russia says they are needed to deter further bloodshed and protect South Ossetia and Abkhazia.
While the U.S. and other Western powers have called for a full and immediate withdrawal of Russian troops, Russia says a peace deal brokered by French President Nicolas Sarkozky allows for "additional security measures" in a buffer zone near South Ossetia, in Georgia proper.