Career diplomat and interim president Kassym-Jomart Tokayev, 66, is running for the ruling party with enthusiastic backing from authoritarian Nazarbayev, who stepped down from the presidency in March.
The 78-year-old strongman's departure shocked Kazakhs who had lived under his rule since Soviet times but he is still expected to call the shots in the oil-rich Central Asian state of 18 million people.
Tokayev has six rivals in the polls that opened at 01:00 GMT including one low-key opposition figure, but none are widely known in Muslim-majority Kazakhstan.
Tokayev, by contrast, has won endorsements from pop stars and film actors, and appears to have the weight of the state machine behind him.
Both men voted early in the capital Nur-Sultan.
After voting at around 04:00 GMT at the lavish state opera house in the capital Nur-Sultan, Tokayev spoke in English with reporters, and acknowledged that Nazarbayev "was still in power in the capacity of chairman of the security council... and other capacities.”
Responding to concerns about police crackdowns on protests ahead of the vote, Tokayev pledged his administration would be "building up a dialogue with all those who support the government and those who are against the government.”
Marat Sagyndykov, a retired 65-year-old former civil servant in the largest city Almaty said he had voted for shoo-in Tokayev "in order to continue the course of the Leader of the Nation,” referring to Nazarbayev's constitutionally designated status.
"I think in 30 years we have had some successes. There have been negatives, too, but they exist in all countries," Sagyndykov told Agence France-Presse (AFP).
Speculating on the outcome of the tightly-controlled vote, Tokayev's campaign chief told journalists Friday that he predicted victory but without the overwhelming backing enjoyed by Nazarbayev.
"I think Tokayev will receive the support of the majority of the population, but to aspire to the figures that Nursultan Nazarbayev received would be inappropriate," said campaign chief Maulen Ashimbayev in comments reported by Russian news agency Interfax.
One of the two Kazakh polling agencies permitted by authorities to operate in the run-up to the vote found Tokayev would win nearly 73% of the vote.
Four years ago Nazarbayev scored nearly 98% of a virtually uncontested vote where the official turnout was 95%.
No Kazakh vote has ever been recognized as fully democratic by the Organization for Security and Cooperation in Europe (OSCE), which has sent more than 300 observers to monitor this election.
Transition 'an illusion'
One of Tokayev's first acts after taking over as interim president was to propose that the capital Astana – which Nazarbayev transformed from a steppe town into a million-strong city – be renamed "Nur-Sultan" in honour of his mentor.
Ivan Sedov, a 42-year-old entrepreneur from Almaty said he had voted for Daniya Yespayeva, 58, the only woman on the ballot "in the spirit of protest...and so that no-one else votes for me."
"I don't support this power transition. I think it has been rushed through. There aren't any (real) candidates to choose from," Sedov told AFP.
There is only one openly opposition candidate in the race, journalist Amirzhan Kosanov, who has a track record of criticizing the government.
However, he has come under fire for a lackluster and tepid campaign where he has vaguely criticized the system, rather than attacking either Tokayev or his predecessor directly.
The buildup to the vote was marked by an intensifying crackdown on the opposition with courts sentencing protesters to short stays in jail and police raiding activists' homes.
Human Rights Watch called the prospect of a genuine political transition "an illusion" and noted the persistence of rights abuses under Tokayev's presidency.
"Kazakh authorities routinely break up peaceful protests, forcibly round up participants – sometimes literally binding their hands and feet – and sanction them with warnings, fines, and short-term imprisonment," the watchdog said.
Nazarbayev's foreign-based political nemesis, fugitive banker Mukhtar Ablyazov, called for protests in cities across the country on Sunday and Monday. – Rappler.com