Igor Demidenko was born on 18 August 1967 in Bobruisk, Mogilev region. In 1988, he graduated from the Poltava Higher Anti-Aircraft Missile Command School. In 2006, he completed the Command and Staff Department of the Belarusian Military Academy (with honours and a gold medal). In 2010, Demidenko graduated from the Military Academy of the General Staff of the Russian Armed Forces.
In 1988–2012, Demidenko served in various positions in the Armed Forces of the Soviet Union and the Republic of Belarus. In 2012–2014, he served as commander of the operational-tactical command, Belarusian Air Force and Air Defence.
On 21 December 2016, Igor Demidenko was appointed to the post of the First Deputy Minister of State Authority for Military Industry of the Republic of Belarus, following Presidential Decree No. 473.
Prior to his new appointment, Igor Demidenko was the head of the Main Military Inspection, Belarusian Armed Forces since December 2014.
Igor Demidenko is married and has two children: a son and a daughter.