Oktay started his riding carrier with Ibrahim Murat. In 2002; Oktay Sezek was third in Istanbul Championship in Junior riders. In 2003, he finished Istanbul championship in C category in the 3^rd place. The same season; Oktay was 4^th in Turkey Championship on El Dorado The year 2008, he was one of the best 4 riders in Regional Championship among B category riders, and he had the same performance at Turkey Championship and placed 3^rd and 4^th. Oktay was trained in army for 1 year in about equestrianism.  After, he also trained and worked with National Senior rider Hulki Karagulle for three years. He successfully finished FEI Level 1 Coaching Course in March 2009. Oktay Sezek is riding for SIEC Since April 2009.

In June 2011 Oktay Sezek reached his first National Team experience in Bojourishte Bulgaria at the CSIO2*-W show and represented Turkey in the Nations Cup and the team got the 3rd place.