The country's Central Election Commission said that there had been a record turnout of 95.11% for the poll.
The result, giving 74-year-old Mr Nazarbayev a fifth consecutive five-year term, had never been in doubt.
The president has promised economic and social stability in the oil-rich Central Asian state.
He ran virtually unopposed as his two opponents were both seen as pro-government.
Human rights groups accuse the authorities of systematically repressing the opposition.
Mr Nazarbayev cast his ballot to loud cheering in the capital Astana, saying he was sure that the people of Kazakhstan would support his campaign.
"I am sure Kazakhstan's people will vote primarily for the stable development of our state and the improvement of people's lives, as well as the stability of the state and in support of the policies the country has implemented under my leadership," he told journalists.
"I am confident of this."
Many voters waited in long queues at polling stations in Astana and in the largest city, Almaty - with many citing a "civic duty" to vote.
Correspondents say that the vote has taken place against a faltering economy in recent months in Kazakhstan, which is the richest of the five former Soviet Central Asian states.
Domestic producers have been dismissing workers as they struggle to compete against Russian imports made cheaper by the weakening of the sanctions-hit rouble.
Elections had been due in 2016, but President Nazarbayev announced they would be held a year early in what some see as a move intended to halt speculation about any possible successor.
A former Communist politburo member, Mr Nazarbayev has been president of Kazakhstan since before it became independent in 1991 following the break-up of the former Soviet Union.
Some 9.5 million people were eligible to vote in the vast country, which has extensive borders with both Russia and China.

Mark Carney told the Guardian the financial sector could be worth 20 times the UK's economic output in 25 years.
He said: "If the UK financial system thrives in a post-Brexit world... it will be 15 to 20 times GDP in another quarter of century.
"Well then you really have to hold your nerve and keep the focus."
Carney was speaking to the Guardian to mark the 10th anniversary of the start of the global financial crisis in August 2007.
He said the UK could not return to the pre-crisis light-touch regulation in order to attract business after leaving the EU.
The governor has previously said the UK after Brexit could be the "investment banker for Europe".
He said: "We have a financial system that is [now] ten times the size of this economy… It brings many strengths, it brings a million jobs, it pays 11% of tax revenue, it is the biggest export industry by some token… all good things.
"But it's risky."
"We have a view… that post-Brexit the level of regulation will be at least as high as it currently is and that's a level that in many cases substantially exceeds international norms.
"The problem you have is that the same issues re-emerge under different labels… and the progress that's been made… is gradually chipped away."
Mr Carney's comments come as US regulators begin formal proceedings to loosen regulations brought in after the financial crisis to curb the way banks took high-risk bets on the financial markets.
Kazakh President Nursultan Nazarbayev has had a widely expected crushing election victory, with early results showing he has won 97.7% of the vote.
[NEXT_CONCEPT]
The governor of the Bank of England has said the banking sector could double in size but still needs tough regulation.