The plan, approved Wednesday, is expected to go into effect within a few weeks.
Opposition Nationalist Party lawmakers have vowed to repeal the law and revoke all citizenships sold if their party returns to power.
Prime Minister Joseph Muscat predicted that selling citizenship will bring 30 million euros into government coffers annually and help ease the country's deficit.
In Brussels, European Union spokesman Michele Cercone noted that Malta and other member states have full sovereignty to decide how and to whom they grant nationality.
The European Court of Justice has on several occasions confirmed the principle of international law that it is for each member state to lay down the conditions for acquisition of its nationality.
Anyone 18 or older will be able to become a citizen of Malta, which has a population of 418,000. Due diligence will be given to applications, such as criminal background checks, but neither investment on the island nor residency will be required.
Purchasers are entitled to buy Maltese passports for immediate relatives for 25,000 euros.
The Labour-led government has said it won't publish the names of those buying citizenship, but the political opposition has said it will if possible.
The prime minister has said the new way to acquire citizenship will attract wealthy individuals "who can help change Malta's economy."
A private company entrusted by the government with promoting the citizenship purchase estimated that there will be some 200-300 buyers each year.
Opposition leader Simon Busuttil called the amendment's passage by Parliament a "black day for democracy" and raised the possibility of a petition drive to force a referendum on repealing the law.
AP writer Raf Casert in Brussels contributed to this report.