A joint session of both houses of parliament approved the change today to exempt the country's first president from a bar on holding the post for more than two terms in a row.
The change was introduced into proposed legislation that Nazarbaev said this week would strengthen parliament's powers at the expense of those of the president.
Nazarbaev touted those changes as an effort to liberalize his post-Soviet republic's political landscape.
Backers argue that the reforms will provide stability in potentially volatile times.
"I don't think [constitutional changes are being made] in [Nazarbaev's] interests, but rather in the interests of the state -- because we're heading toward difficult times. And we shouldn't yield to euphoria, because the country is going to see problems among political parties as well as ethnic groups increase as parliament is given such [additional] powers," Amangeldy Aitaly told journalists after today's vote. "Therefore we will need a wise leader with a great deal of experience."
The package of reforms included a proposal to cut the presidential term from seven to five years as of 2012, when Nazarbaev's current, second term expires. He has ruled the country since 1989.
"A group of [parliament] deputies...proposed adding the following words to Paragraph 5 of Article 42 of the constitution: 'This norm does not apply to the first president of the Republic of Kazakhstan,'" upper house lawmaker Ermek Zhumabaev said. "Considering the first president's historic role in the formation of our state, as one of the founders of a new, independent Kazakhstan, as well as the need to complete the initiated political and economic reforms, the joint commission accepted this proposal."
The legislation now goes to Nazarbaev for signing.
(Reuters, AFP, Interfax, RFE/RL's Kazakh Service)