Iliev spent his early years with his hometown club Balkan Botevgrad, before joining Vidima-Rakovski's youth academy in 2006.

[6] On 5 June 2015, Iliev moved abroad for the first time, agreeing to a three-year deal with Romanian Liga I club FC Botoșani.

On 11 October 2011, he was sent off in the last minute of Bulgaria's 3–2 win against Luxembourg U21 in a 2013 UEFA European Under-21 Football Championship qualifier after an altercation with Tom Laterza.

Iliev received his first call-up to the senior team of his country in 2011[14] and made his debut on 29 May 2012, in the 0–2 loss against Turkey in a friendly match after replacing Stoyan Kolev in the 76th minute.

[15] Iliev appeared as a starter for the first time in the 2–1 win over Kazakhstan in another exhibition match held on 4 June 2013, managing to keep a clean sheet, with Bulgaria conceding after his replacement.

[16] On 31 August 2017, he saved a penalty taken by Emil Forsberg and the subsequent shot from the rebound in the 16th minute of the game in a historical 3–2 home win against Sweden.