Career
Kostadinov started his career at Naftex Burgas before joining Chernomorets Pomorie in 2009. On 16 January 2012, he signed for Razgrad. His A Group debut was on 18 March, as a substitute against Svetkavitsa, replacing Stanislav Genchev in the 78th minute.
Six minutes later he scored his first goal, netting the fourth in a 5–0 victory.
After his contract with Beroe expired, Kostadinov joined Levski Sofia. On 3 July 2015, he signed a two-year contract with Levski.