NCOC serves as the operator of Kashagan, representing a consortium that includes ConocoPhillips, Exxon Mobil, French energy company Total, national energy company KazMunayGas, Royal Dutch Shell and Japanese oil company Inpex.
"The first well was opened and the initial volumes of oil are being produced from the Kashagan field," the company said in a statement.
Italian energy company Eni holds a 16.8 percent stake in the consortium and is tasked with starting production at the field.
"In the initial phase output will grow up to 180,000 barrels per day," Eni said in a statement. "Afterwards, the production will increase progressively up to 370,000 barrels of oil equivalent per day."
NCOC said Kashagan is the largest oil field in the North Caspian Sea with an estimated 35 billion barrels of oil in place.
NCOC said its oil transit options include exports to the 28-member European Union and oil-hungry China where demand is expected to increase significantly this year.
The International Energy Agency said oil exports from Kazakhstan should more than double by 2035.
Kashagan was discovered in 2000.