The sale to a number of Qatari investors would generate a profit of $87 million, which would reflect in 2014 financial results, NBK said in a statement.
It remains subject to the standard regulatory approvals.
Chairman Nasser al-Sayer said NBK exited from the investment, made a decade ago as part of the bank's regional expansion strategy, after it saw limited opportunities to increase the 30 percent ownership in IBQ to a controlling stake.
Signup to our newsletter and follow us on Facebook and Twitter!
"This sale will also strengthen our capital position to pursue our regional expansion strategy and benefit from any opportunity in Qatar or any of the other GCC (Gulf Cooperation Council) markets," Sayer said.
NBK acquired a 20 percent stake in IBQ in 2004 and increased it to 30 percent three years later. It had also been managing the bank.
NBK was founded in 1962 and its assets stand at around $66 billion. It has around 170 branches in the Arab world and in foreign cities, including New York, London, Paris and Geneva.