Kazakhstan's Foreign Ministry spokesman Anuar Zhainakov told CNN the Syrian opposition delegation had arrived at the capital Astana ahead of the talks. Representatives of Syria's government are due to arrive later.
"I can confirm that the delegations from Russia, Turkey, Iran, (UN Special Envoy for Syria) Staffan de Mistura and the Syrian opposition delegation are all in Astana already," said Zhainakov.
Russia and Turkey led efforts on these latest Syria peace talks, after Syrian rebels suffered a major defeat in December of last year by losing control of districts of eastern Aleppo they had held for nearly four years.
The rebels' loss followed an air bombing campaign by Russia that turned the tide of the war in favor of Syrian President Bashar al-Assad.
Syria's brutal civil war has raged on for nearly six years and killed an estimated 400,000 people
On December 29, Russian President Vladimir Putin announced an agreement in which the Syrian government and opposition rebels would cease fighting.
Putin said the two sides agreed to enter peace talks to end the conflict, according to the Russian state-run TASS news agency.
Putin and Assad described the Astana talks as "an important step towards a final crisis resolution" according to a statement by the Kremlin
Although Russia and Turkey brokered the agreement, the two countries have differed in their stance on Assad, whose family has ruled Syria for four decades.
Turkish President Recep Tayyip Erdogan reportedly said in November
that Turkish forces entered Syria to help end Assad's rule. Meanwhile, Russia is Assad's most powerful ally and has propped up his regime since September 2015 with airstrikes.
The United States, which led previous peace talk efforts, was invited to attend the talks in Astana, but declined to send a delegation, according to acting US State Department spokesman Mark Toner in a statement issued Saturday.
Toner said the decision not to send a delegation was due to the inauguration of President Donald Trump and the "immediate demands of the transition" and that US Ambassador to Kazakhstan George Krol would instead represent the US "as an observer."
"The United States is committed to a political resolution to the Syrian crisis through a Syrian-owned process, which can bring about a more representative, peaceful, and united Syria," Toner said in the statement.