The decree was adopted by the ruling Syriza party and its junior partner ANEL by 156 votes in favour and 104 against in a noisy debate.
The decree says the reserves will be used to cover "the state's urgent needs, which amount to three billion euros over the next 15 days".
As talks bog down between Athens and its international creditors to unlock 7.2 billion euros (USD 7.7 billion) in bailout funds, the cash-strapped leftwing government last week moved to call in reserves, triggering a wave of anger.
It underlines the urgency of the cash crunch faced by Athens and heightened fears that Greece was lurching closer to defaulting on its debt and a potentially chaotic exit from the eurozone.
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The government estimates the move will raise some 1.5 billion euros, but local media have put the figure at around 400 million euros.
Local authorities have complained bitter about the government decree, warning that the raid on their reserves could bring public services to a halt.
But Mardas defended the government's move as "no more than a short-term loan by the state", adding that the funds would be reimbursed "according to the needs, within a period of 15 to 20 days".
Meanwhile in Riga on Friday, the eurozone's 19 finance ministers ended a meeting without a breakthrough towards unlocking bailout cash, with the threat of a messy exit by Greece from the euro still hanging in the balance.