[6] Iliev appeared three times in the Arsenal squad as an unused substitute: against Norwich in the Carabao Cup in October 2017; and twice in the UEFA Europa League: against Qarabağ and against Chelsea in the final as the third goalkeeper.
[10][11] In July 2019, he moved to ŠKF Sereď for a one-year loan, and on the 22nd of the same month he made his debut for his new club in the 2–0 loss to Spartak Trnava.
[12][13][14] After an early end to his loan with ŠKF Sereď, Iliev opted to join Polish Ekstraklasa club Jagiellonia Białystok for the remainder of the 2019–20 season.
On 8 October 2020, Iliev joined League One side Shrewsbury Town on a short-term loan deal.
[21] On 1 August 2023, it was announced that Iliev will be ruled out for the rest of the season following an elbow injury suffered in a Veikkausliiga match against SJK Seinäjoki.