Oinarov began his career in 1992 as a junior researcher at the Ministry of Economy of Kazakhstan.
In 1994 he worked as chief specialist at NAFA under the Ministry of Economy, then moved to a similar position in the State Export-Import Bank.
In 1996 he started working for Almaty Merchant Bank CJSC. Then he was appointed deputy chairman of the board of Tsesnabank JSC in 1997.
Between 1998 and 2003, he worked for the Economic Planning Committee of the Ministry of Economy and Trade, the Chancellery Department of the Kazakh Prime Minister and the Agency for Regulation of Natural Monopolies and Protection of Competition.
Between 2003 and 2006 he worked as Deputy Finance Minister and in 2007 he was appointed Deputy Defence Minister for Economics and Finance.
In 2010, he moved to the private sector, to TASK Holding LLP as financial officer, then worked as advisor to the chairman of the Board of Directors.