In 2008, he graduated from the Institute of Philology at Taras Shevchenko National University of Kyiv with a master's degree in English and Arabic translation with honors.

In 2008, Oleh Nikolenko passed a competition for the position of attaché at the Ukrainian Embassy in Libya, where he worked in extreme conditions and was involved in the evacuation of Ukrainian citizens since 2011, when the civil war began in Libya.

After returning from Libya, he worked at the Ministry of Foreign Affairs of Ukraine in charge of the North Africa and Middle East region, and was an assistant to the Special Representative of Ukraine for the Middle East and Africa.

In 2015-2020, he was the spokesperson for the Permanent Mission of Ukraine to the United Nations in New York.

In 2016-2017, he served as a member of the Ukrainian delegation to the UN Security Council during Ukraine's non-permanent membership, where he dealt with North and West Africa, the settlement of the Western Sahara issue, and was the coordinator of the UN Security Council Sanctions Committee on Sudan 1591 (2005).